General Notes Flashcards

Question

What is pitch? What does a pitch < 1 imply? What about > 1?

Answer 1

Table increment per rotation / beam collimation > 1 implies gaps between slices (less dose, decreased image quality) < 1 implies overlapping slices (higher dose, increased image quality)

Answer 2

EMR capture information from a single care provider, which is only available to that one provider and their clinic EHR is designed to be used by multiple care providers and healthcare organiations

Answer 3

HBB and rotate collimator to limit divergence

Answer 4

They're hard to cover with traditional field arrangements, so some sites utilize VMAT to cover all nodes

Answer 5

Solid state scintillators Cadmium tungstate, gadolium based or ceramic scintillator

Answer 6

False Only present in 3rd generation

Answer 7

Either with an isodose map given by the vendor Or with CTDI1000 or DLP applied to an equation. But these are less common

Answer 8

Because at higher MV energies, the buildup cap size required for CPE is so large, that it effectively acts like a mini phantom and the readings are no longer in air

Answer 9

Scatter from jaw backscattering to chamber, reducing dose/MU Scatter from jaws reaching patient, increasing dose/MU as jaws get larger (more surface area to scatter) The 2nd effect is the more dominant

Answer 10

Output factor = AF x CF Applicator factor corrects output between 10 x 10 cm2 to open cone size you're using Cutout factor corrects output between open clinical cone size to cone size with cutout you're using Output factor is the full conversion relative to a 10 x 10 cm2 open cone to your clinical setup

Answer 11

Using the CT component of the PET/CT Algorithm takes into account that peripheral annihilations travel less through tissue, thus attenuate less, meaning that the counts detected will be higher than central, even if true counts are the same

Answer 12

Bladder, kidneys, heart, brain Anything that either clears agents from the body or circulates them The brain has a high glucose intake, so that'll also be naturally bright

Answer 13

* Check for accurate image interpretations (scanned catphan) * Check that patient positioning and orientation is accurately defined * Check that immobilization devices, if available, are modeled in TPS * Commission beam model (TG-106, 119, MPPG 5a) * Calculation and easurement of sample test cases for EBRT or HDR * Check of entire treatment plan normalization and MU calcs on a series of plans * Accurate DVH calculation and construction * Limit testing of algorithms for when they begin to fail in dose prediction * End-to-end testing

Answer 14

Monthly - CT data input verification (Accurate SSDs, spatial representation, CT number vs electron density) Annual - dose calculation accuracy and consistency of all clinically utilized algorithms The purpose to TPS QA in essence is to 1. Make sure there was no unknown changes to the beam model (checked with calc, recalcs and checksums) 2. Make sure there was no unknown changes to electron density curve and image quality

Answer 15

In the linear part, Z is low, so dominant interaction is compton. The compton cross section increases with electron density, however, most soft tissue has effectively the same electron density. The key difference then is physical density, which will increase the linear attenuation coefficient proportionally, hence linear In higher Z region, photoelectric starts to become more prominent, which increases linear attenuation coefficient at a non-linear rate

Answer 16

Radioactive iodine SPECT imaging which assesses thyroid function and potential disease spread Ultrasound which assesses nodule size and visualizes microcalcifications

Answer 17

TG-218 is the main one for tolerance limits and methodologies TG-230 focuses more on dosimetry tools and techniques

Answer 18

Tolerance limits are meant to be a warning that something might be out of the ordinary in the specific plan, treatment system, or TPS. Plans failing to meet tolerance limit should be investigated, but may still be clinically acceptable if they are able to pass the action limit Action limit defines the amount a measurement can deviate from calculation without risking harm to the patient. Plans failing to meet the action limit should be replanned to improve deliverability. 3%, 2mm, 10% minimum threshold Tolerance limit is pass rate >= 95% Action limit is pass rate >= 90% **Note: ** exact same tolerances as what were used at CTCA

Answer 19

It is a factor that converts exposure to absorbed dose **to air.** fair = 0.876 rad/R which is found by noting that 1 R = 2.58 E-4 C/kg and 33.97 J are required to ionizie 1 coulom of charge

Answer 20

Dmed = Dair * ratio of mass energy absorprtion coefficients **Note:** Why is it not ratio of limited mass stopping powers? This is because bragg gray cavity theory and spencer-attix cavity theory is only valid for small cavities, in which only electron fluence contribute absorbed dose to the cavity and photon interactions from in the cavity can be neglected In survey meters, exposure is measured and photons are the ones contributing the dose, thus we talk about the energy absorption coefficient ratios

Answer 21

A digital filter applied to k-space (frequency domain) data that acts to suppress low spatial frequencies Side effect is an increased image noise which is largely contained in the unsuppressed high frequency portion of k space

Answer 22

Decrease pitch, allowing for sufficient data to be collected at all breathing phases Coach patient to try to turn an irregular breathing cycle into a regular one Reposition camera or surrogate device to make sure it's reading an amplitude appropriate to the breathing cycle Manaully re-bin or assign peaks on the respiratory cycle if automatic peak selection fails, which it may for irregular breathing cycles

Answer 23

A barrier consisting of different layers of different shielding material Commonly may be used is lead or steel sandwiched by concrete It is useful in reducing the overall thickness of the barrier, which allows for better space saving

Answer 24

“Medical professionalism is a belief system about how best to organize and deliver health care, which calls on group members to jointly declare what the public and individual patients can expect regarding shared competency standards and ethical values and to implement trustworthy means to ensure that all medical professionals live up to these promises.” In essence, it's a belief system that sets a standard for what the public should expect competency and ethically wise in a medical professional

Answer 25

1. Professional Competence 2. Honesty with patients 3. Patient Confidentiality 4. Maintaining appropriate relationships with patients 5. Improving quality of care 6. Improving access to care 7. Just distribution of finite resources 8. Scientific knowledge 9. Maintaining trust by managing conflicts of interest 10. Processional responsibilities including self-regulation

Answer 26

* **Code of ethics for the AAPM** * **TG-109** * **Hippocratic Oath** * Declaration of Geneva * Good medical practice - UK * AMA Code of Medical Ethics

Answer 27

1. Data acquisition and processing 2. Model creation 3. Validation of model 4. Establishment of ongoing QA program

Answer 28

Typical workload is 500 Gy/wk But you want to consider your own clinic practices, primarily * How many patients are treated per week * What are the typical prescriptions given? * How much QA is performed in a given week? * Are there any special procedures (especially TBI)?

Answer 29

To minimize gradient effects across the reference cylindrical ion chamber

Answer 30

Process tree mapping --> FMEA --> Fault tree analysis --> development of mitigation strategies

Answer 31

Evaluates how failure propagate through a process, and helps identify mitigating strategies for a given failure

Answer 32

Kind of both... On one hand, you're evaluating the current status of treatmen tparameters, compared to tolerances, and making adjustments if they fail. Thus you can argue it's QC On the other hand, most reports refer to them as QA, and you are demonstrating whether a safe and successful treatment or a correctly functioning machine is being output

Answer 33

The vendor outlines acceptance testing procedures but these can be negotiable prior to purchase and specified in the purchase agreement

Answer 34

Safety --> mechanical --> radiation --> imaging

Answer 35

The waveguide carries RF power to the accelerator waveguide by propogating the energy based on the conductive walls of the waveguide tube, which acts as distributed inductors. The space between the walls acts as capacitors Arcing is an occurence in which electricity from one conductor jumps to another, causing a flash of electricity SF6 is a dielectric, which acts as an insulator preventing the arcing from discharging in the waveguide

Answer 36

Fill gas would cause energy degradation and unbunch the electrons

Answer 37

National Academy of Science Biological Effects of Ionizing Radiation

Answer 38

Most of it is from atomic bomb survivors But the BEIR study includes data from people exposed for medical reasons and nuclear workers

Answer 39

Because at low doses, the probability increase for radiation induces cancer is so low, that it is very difficult to distinguish against all other environmental and genetic factors

Answer 40

Activation of enzymatic DNA repair Apoptosis (programmed cell death) Cellular signaling of radiation damage to initiate nearby cells to activate defenses and attack damaged cells

Answer 41

%DD(10)x increases with increasing beam energy As beam energy increases, the water to air stopping power ratio decreases, which reduces kQ

Answer 42

Simply the central axis of the chamber

Answer 43

Minimizes impact of gradient effects within the sensitive volume which impacts depth-ionization curves

Answer 44

Because POM is used to align the chamber at the ADCL, not EPOM

Answer 45

Hiring a freelance editor is appropriate, however, you must take appropriate cre to ensure that no confidential information is disclosed to the editor Assuming the editor's only role was to edit the draft, they should not be listed as an author. However, they should be acknowledged as a contributor to the manuscript

Answer 46

If all the nurse contributed was recruitment, that is not grounds for authorship. However, they should absolutely have been acknowledged in the final paper. In this scenario, you should express your apologies for excluding them in the acknowledgements and emphasize their importance in the study, while also being firm and respectful in your decision that they should not be listed as an author

Answer 47

1. Contribute substantially to the concept or design of the study. Including data acquisition, analysis, OR interpretation of analysis 2. Draftng the work or revising it critically for important intellectual content 3. Approval of final version to be published 4. Agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of the work are appropriately investigated and resolved

Answer 48

An authorship conferred without fulfilment of the authorship criteria Honorary authorship is never appropriate

Answer 49

If personnel is likely to receive more than 10% of their annual exposure limits Or if they declare pregnant Or any individual entering a high or very high radiation area Ring badges are different, and are usually only worn by individuals who handle radiation sources or work in fluoroscopy

Answer 50

Demonstration that none of the workers is likely to receive 10% of dose limit This is demonstrated by use of area surveys, or previous experience monitoring workers in similar environments A calculation may also be performed

Answer 51

ALARA 1: 10% of quarterly limit exceeded. Should be brought up at next RSC meeting, and discussions should be had if that level of exposure is appropriate for that individual. If so, no further action ALARA 2: 30% of quarterly limit exceeded. Investigation by RSO to determine cause of exposure, in addition to actions that may be taken to mitigate future exposure. Results should be reported to RSC ALARA 3: 40% of quarterly limit exceeded. RSO will supply RSC with written documentation about how to reduce dose ALARA 3b: 70% of quarterly limit exceeded. RSO required to take action to change person's work environment until end of the year

Answer 52

It should decrease computation time. Threshold dose is used to assume the point at which a particle is so low energy, it cannot escape a given voxel and thus deposits its remaining energy into said voxel. Increasing threshold dose will decrease accuracy, but also decrease treatment time since you're ending particle histories a bit earlier

Answer 53

Up until the ion chamber Anything above the ion chamber is assumed to be constant for every patient

Answer 54

If you have a detector that is calibrated to give dose in both the reference condition and the non-reference small field condition This usually doesn't exist, since calibrated detectors are typically ion chambers which are not good for small field dosimetry

Answer 55

Chambers below 0.05cc are expected to have higher noise, and unuaul polarity and recombination behavior and are also typically impacted by irradiation history

Answer 56

A plan is considered "Pareto-Optimal" when it is not possible to improve the plan with respect to one objective without worsening it with respect to another objective. That is, when the plan is as good as it can be without making a trade-off

Answer 57

A "Pareto-Surface" is the st of all Pareto-optimal plans which are generated by optimizing, usually by direct machine parameter optimzation, to produce a set of Pareto-Optimal plans These plans are then interpolated providing the set of plans along the surface

Answer 58

* Must assure that the quality of published work meets journal's standards * Provide an unbiased, independent, critical assessment of the manuscript * Must be technically proficient in the area they are reviewing * Should provide feedback that is constructive and polite, while also being honest and forthcoming * Should not be influenced by conflicts of interest

Answer 59

Double blind The author doesn't know who the reviewer is The reviewer doesn't know who the author is This allows for honest feedback without fear of retaliation, while also limits the personal bias a reviewer may have of the author

Answer 60

Submission of substantially similar manuscripts and publication of said manuscripts multiple times or the simultanous publication of a single manuscript in multiple journals

Answer 61

No This is generally acceptable "secondary publication." But it is recommended that full disclosure of the original abstract be in the final publication

Answer 62

RSO Member of nursing staff Representative from management who is neither RSO nor AU And an AU for each byproduct material listed on the license

Answer 63

RSC typically meet quarterly Most meetings include... * Review of minutes from previosu meeting * Review exposure or incidents * Review recent and upcoming radiation safety program events, surveys, etc * Update roster of committee members * Plan for institutional and equipment changes

Answer 64

Any site that is authorized for two or more different types of byproduct materials So I site only involved in I-131 treatments, does not need an RSC, BUT still needs an RSO

Answer 65

* Be certified by an NRC approved specialty board * Hold a masters or doctorate degree in physics, medical physics, physical science, engineering or applied mathematics

Answer 66

Increased obliquity will... Decrease depth of max dose Decrease therapeutic depth Increase Dmax Increase surface dose Increase practical electron range

Answer 67

In principle yes, but in practice no since kq values are not listed in TG-51 The addendum also recommends that only cylindrical chambers be used as there is insufficient information about wall correction factors in photon beams other than Co-60

Answer 68

Yes In fact they may even be BETTER than cylindrical chambers

Answer 69

Because plane-parallel chambers can be very sensitive to small changes in their constructions, including those can can occur due to rough handling during transportation

Answer 70

To minimize gradient effect across cylindrical chamber

Answer 71

This does qualify as a conflict as interest as there is an ongoing financial relationship with the hotel This may or may not pose an ethical issue. Context matters. If the arrangement provides a real benefit to the patients by lowering the cost of stay and still allows for hospital to provide information about other hotels, than this is acceptable. But if anything is done to place the patient at potential financial risk, it becomes unethical

Answer 72

A US Federal law preventing physicians from self-referral. That is, referral to a service in which themselves or a family member has a financial relationship with

Answer 73

Seeks to pair voxels of a given intensity in image A, with voxels of a corresponding but uniform, but not necessarily similar, intensity in image B. That is, it is able to consider matching all light voxels in image A to dark voxels in image B, provided that the shape and size of the voxel areas is similar

Answer 74

Because the interleaf leakage is in the same plane as the rotation of the arc. This will yield larger leakage radiation in plane

Answer 75

A report that defines ethical principles and guidelines for research involving human subjects

Answer 76

1. Respect for personons Protecting autonomy of all people and treating them with courtesy and allowing for informed consent 2. Beneficence Do no harm. Maximize the benefits of the research while minimizing the risks 3. Justice * Ensure reasonable, non-exploitive, and well-considered research procedures * Ensure fair distribution of costs and benefits to potential research participants * Ensure research participants are treated equally

Answer 77

Institutional Review Boards Committee that oversees research, especially that involving human subjects. Are responsible for assuring research on human subjects is conducted in a manner that is scientific, ethical, and comply with all relevant regulations

Answer 78

In scenario A, there's really nothing to do. Pd-103 is very low energy, so the toilet water will absorb pretty much all the dose. At that point, flush the seed in the toilet. It may be beneficial to get an idea of the scenario from the patient as well, how many seeds? In scenario B, you should place the seed in a shielded container and allow it to decay for 10 HLs prior to disposal. You should also ask the patient how they carried the seed, and inform them of any side effects and increased risk of exposure they may expect

Answer 79

Approximately 9% of LDR prostate patients experience seed migration. Of these 9%, 75% are lost through the urethra, 25% become lodged in the lungs after migrating through prostativ veins

Answer 80

No, mean energy is not the same as nominal energy. Nominal energy is the electron beam mean energy as it exits the bending magnet. However, the electron beam will degrade through the scattering foil, air, treatment head, and cone. Along this path, the mean energy will drop Mean energy is defined at patient/phantom surface, and is found by 2.33*R50

Answer 81

Depth of max dose is reduced Relative skin dose increases Decrease the slope of dose falloff

Answer 82

1. 90 deg bending magnet, not commonly used 2. 270 deg bending magnet, used by Varian 3. Slalom type bending magnet, used by Elekta

Answer 83

Well chamber

Answer 84

TG-40 Most recommended tests are done initially when the well chamber is acquired, or after repairs of the well chamber. These include (do not memorize these)... * ADCL calibration * Precision * Linearity * Collection efficiency * Geometrical/length dependence * Energy dependence * Source wall dependence * Venting Others include a redundancy check, which is done with another well chamber whenever you would use them (source exchange), tolerance is 2%. Another is a leakage check which is done whenever you would use the chamber (source exchange). These you should probably know

Answer 85

HDR 1000 Plus (standard imaging) 245 cc 300 V 10 mins to stabilize after being plugged in Outside body is aluminum It's vented (requires TP correction)

Answer 86

Extremely small volume Minimal perturbance of underlying dose distribution Allowfor instantaneous readout Some MOSFETs provide permanent dose record

Answer 87

Finite lifespan of about 100 Gy Strong temperature dependence Energy dependence Sensitivity changes with integral dose as trap centers fill

Answer 88

Metal Oxide Semiconductor Field Effect Transistor Consists of three leads, a source, the drain , and the gate When voltage applied to the gate is too low, the region between the drain and source contrains excess electric charge, peventing current flow. When voltage applied exceeds threshold voltage of the gate, current is able to flow. When a MOSFET is irradiated, holes are created in a SiO2 layer underneath the gate, separated out, and increase the threshold voltage of the drain

Answer 89

An event not caused by patient intervention in which dose differs from prescribed dose by more than 50 mSv effective dose equivalent, 500 mSv organ or tissue dose equivalent, or 500 mSv shallow dose to the skin AND one of the following * Total dose delivered difference of 20% from prescription * Single fraction dose delivered difference of 50% from prescription * Wrong radioactive drug was administered * Wrong route of administration * Wrong individual received the intended treatment * A leaking sealed source * Wrong mode of treatment

Answer 90

Physician determines when/if to inform the patient Physicist may be brought in the consult with patient regarding... * Nature of error * Expected impact of event Physicist must be careful to speak only within their scope of expertise, and provide contact information should the patient have questions later It is important to speak honestly but with empathy for the emotions of the patient

Answer 91

* Noticy NRC operation center no later than the next calendar day * Inform physician within 24 hours of discovery * Physician then informs the patient at their discretion * Generate a written report and submit to NRC within 15 days

Answer 92

Pacemakers send small electrical signals to the heart muscles that regulate heartbeat for treatment of bradycardia (low heart rate) or irregular hearbeat Defibrillators use a capacitor to deliver a high voltage shock to the heart when the device detects ventricular tachycardia (abnormally fast heartbeat)

Answer 93

Deactivates tachycardia sensing mode of the the defibrillator This is important because during RT, the dose rate may increase reading of the defibrillator, and trick the defibrillator into thinking tachycardia is occuring, thus false shocking the patient

Answer 94

Identify type and model of device, and contact vendor for guidance/recommendations Contact cardiologist or electrophysiologist to get status of dependence of patient, if a magnet can be placed, and when most recent interrogation occured Do not treat beams entering or exiting device Use energies 10 MV or lower Keep cumulative dose below vendor and TG 203 recommendations Follow TG 203 guidance to estimate dose to pacemaker, and to classify risk level for patient Given risk level, follow TG 203 and clinic specific policy for practices during treatment course, including device interrogation scheduling with cardiology team

Answer 95

Advantages: * Uses actual treatment geometry * Displays block/MLC positions relative to treatment anatomy * If used as during imaging, that is, delivered with the beam, will contribute no extra dose to the patient Disadvantages: * Worse contrast * If not delivered with the treatment field, it contributes more dose than kV planar

Answer 96

Most common design consists of a metal copper plate (1 mm thick) which attenuates the photon beam, emitting electrons These electrons are incident on a phosphor screen which emits scintillation photons The scintillation photons are detected by an amorphous silicon panel which converts photons to electric signal

Answer 97

Daily * Collision interlock functionality * Positioning/repositioning accuracy * Imaging and treatment coordinate coincidence at single angle Monthly * Imaging and treatment coordinate coincidence at 4 cardinal angles * Image scaling * Spatial resolution * Contrast * Uniformity and dose Annual * Full range of travel SSD * Imaging dose

Answer 98

FLOPS are floating point operations per second, which is the measure of the computation speed of a computer Clock speed refers to the rate at which logic gates are able to change state Floating point operations refer to arithmetic operations using formulaic expressionf of real numbers. These are similar to scientific notation. It requires less memory for very small and very large real numbers, resulting in less memory requirement and quicker operations. However, it also introduces rounding error as they are approximations of real numbers

Answer 99

**Traveling Waveguide** EM wave progresses longitudinally through cavity, any remaining energy of the target end of the waveguide must be absorbed. Electrons are accelerated down waveguide in manner similar to surfer. Pros: less expensive Cons: Generally longer and less stable Vendors: Elekta **Standing Waveguide** Microwave electric field changes its amplitude vs time, rather than its position. Energy remaining at the end of the waveguide is allowed to reflect backward. Forward traveling and backward traveling waves produce a net stationary waveform which oscillates in sign vs time. Nodes (which are cavities with zero electric field at all times), are fixed and never provide any acceleration and can be side coupled which allows for a shorter waveguide. The microwave still passes through these side couples on it's way to the rest of the cavities, however the electron doesn't have to, meaning waveguide can be shorter. Pros: Shorter, more energy efficient, more stable beam Cons: More expensive Vendors: Varian and Siemens

Answer 100

By increasing or decreasing the number of electrons in a bunch Electrons must share the microwave energy present. So more elctrons means less energy per electron

Answer 101

Superior border is top of skull Inferior border is at least 5 cm beyond PTV (typically T7ish is more than enough)

Answer 102

* When do changes occur? How early in the course are we? * Is surface changes greater than 1 cm? How much of an effect will that make on raw TMR calcs? * Are anatomical changes causing target and/or OARs to move relative to PTV and/or OAR contours? * Are we losing ability to reproducibly immobilize/position patient?

Answer 103

HIPAA requires that a PACS system has procedures to protect and secure patient data That means that the system is secured against inappropriate access (Ex. password gating) and that date should be encrypted. It also requires that data must be secured against unintentional or intentional destruction, usually via off site backup and/or offsite DICOM server mirroring

Answer 104

Both are ways to store copy of data, main difference is time frame Backup is a scheduled task in which data is copied at regular intervals Mirroring is a near real time, as data is stored, moved or deleted from the primary server, the mirrored data is a near exact copy of the main server data at any given time

Answer 105

Fluence map optimization creates a fluence map which produces a dose distribution that minimizes cost function to true global minima. The planning sytsem then attempts to create setup points to produce the fluence map. The cons of this are that the optimized fluence map may not match the actual planned fluence map due to machine limitations. The pro is that it is a quicker optimization calculation Direct machine parameter optimization considers machine parameters during the optimization process. It's slower, and will lead to local optimal solutions, requiring simulated annealing. However, the resulting fluence map and control points from the optimization plan will better resemble the deliverable plan

Answer 106

Analytical Method and Iterative/Stochastic method Iterative/Stochastic method is used in Eclipse

Answer 107

Yes, two types of exceptions 1. Planned special exposures, the limit being 50 mSv added to the annual limit in which those 50 mSv come from the planned special exposure itself. Worker must be informed about the dangers and scope of their work 2. Emergency action exposure. These are NOT regulated by the NRC, provided that they are necessary to protect health and safety. EPA gives a recommendation of < 100 mSv to protect infrastructure, and < 250 mSv for life saving activities, but these are guidelines not regulation

Answer 108

10 CFR 20 provides an exception to this requirement if the room is within a hospital or clinic, access to the room is controlled, and prsonnel take necessary safety precautions

Answer 109

10 MV: 6 mm Co-60 teletherapy unit: 15 mm (due to larger source size) Linac source size is 1 mm. Co-60 teletherapy unit source size is 1-2 cm2. Which greatly increases geometric penumbra, even despite shorter SAD

Answer 110

Decreases with increasing energy

Answer 111

5 - 7 cm of lead, which is about 4 - 5 HVLs Pros: Reduces fetal dose by > 50% Cons: difficult to construct and increases treatment time

Answer 112

1. Estimate dose to fetus and have an open and honest conversation with the patient regarding potential risks to the fetus 2. Consult with physician regarding if remainder of treatment can be pushed until after baby is delivered. Consider how far along the patient is and how aggressive the disease is 3. If plan will be continued, consider planning strategies to reduce dose as highlighted by TG 36. Including shielding bridge and dose monitoring

Answer 113

ALI is limit of amount of radioactive mateirla taken into body by inhalation or ingestion per year It's determined on a nuclide-by-nuclide basis such that the "reference man" would receive a committed whole body dose equivalent of 50 mSv/yr or a organ/tissue of 500 mSv/yr Found in 10 CFR 20 appendix

Answer 114

A concept used in dosimetric calculations by the NRC and ICRP It's a standardized, caucasian male between ages of 20 - 30 with an average weight and height

Answer 115

A model of the primary photon fluence incident on the patient is generated for each beam/control point Ray tracing projects the fluence distribution through the patient TERMA is then computed as the product of fluence and mass attenuation coefficient through a given voxel. That product is inherently the energy released in that voxel

Answer 116

A kernel represents the energy spread resulting from radiation interactions at a given point

Answer 117

Yes Multiple kernels make up a single kernel. These kernels correspond to different photon energies, and have relative weighting depending on the depth and expected energy spectrum at a given depth

Answer 118

Superposition Kernel tilting

Answer 119

It models the kernel as a finite number of rays emitted from the point of interaction, rather than as a continuous 3D object Results in a loss of accuracy far from point of interaction

Answer 120

As electrons reach the catcher cavity, they induce a retarding electric field, which causes additional electrons to decelerate quickly This deceleartion releases energy at the microwave frequency at a much higher amplitude than that input into the buncher cavity

Answer 121

Magnetrons > Klystrons * Smaller * Simpler * Cheaper * Produce their own microwaves Klystrons > Magnetrons * Have longer life expectancy (approx 5x longer) * Can produce a higher power output

Answer 122

1. Initial onset of symptoms 2. Temporary reduction in symptoms 3. Increase in severity of symptoms (most severe stage) 4. Death or recovery

Answer 123

Most likely yes. Especially without immediate medical intervention Above 8 Gy whole body exposure, the probability of survival is very very low Cause of death is most often infection due to leukopenia (drastic drop in disease-fighting leukocytes). Bone marrow transplants can improve survival chances

Answer 124

TLDs are crystals doped with lithium fluoride Irradiating TLD creates electron-hole pairs Electrons are carried into the conduction energy band to electron traps, caused by impurities in the crystalline structure Holes migrate to a hole trap via the valence energy band The pairs are stored in their respective traps until readout Readout is accomplished by heating the TLD which imparts enough energy to the electrons that they are able to escape their trap centers Once free, the electrons enter recombination/luminescent center swhere theye mit luminescent photons The photons are measured by a PMT or camera

Answer 125

Yes Competitive centers (trap centers that do not contribute to luminescence) fill up through TLD exposure, but are not emptied by annealing This means that with each TLD use, there are less competitive centers, which means the sensitivity of the TLD increases (supralinearity)

Answer 126

OSLD Pros * Can be read out multiple times * Fade much less than TLDs * Readout and annealing is quicker OSLD cons * Made of an aluminum oxide, which is less tissue equivalent than TLDs, meaning more energy dependence

Answer 127

A domain-specific language used to manage actions within a database

Answer 128

TD5/5 is the dose delivered to normal tissues that causes a 5% adverse reaction rate over 5 years This dose level is often chosen as the dose level to evalute therapeutic ration in RT studies

Answer 129

because normal tissue, which has a lower alpha/beta, benefits more from sublethal repair than tumor cells

Answer 130

An organ in which many or all of the sub-units must be disabled to cause organ failure

Answer 131

Equivalent Uniform Dose It's defined as the absorbed dose that, if homogeneously delivered to an organ, causes the same expected number of cells to survive as the actual non-homogenous absorbed dose

Answer 132

Serial organ: alpha around 10 (approximates max dose constraint) Parallel organ: alpha of 1 (reduces to mean dose) Target: alpha of negative value

Answer 133

MPPG 8 This test is not mentioned in TG-142. Only to test functionality Tolerance is +-3% from baseline

Answer 134

Physical wedges can increase out of field dose by a factor of 2 or more depending on angle and mounting position EDW barely increases out of field dose

Answer 135

* This is the ACR 464 CT Phantom * Module D is used for spatial integrity (in addition to uniformity). It's really hard to see, but there's two small objects that are diagonally 10 cm away from each other * Module B has 5 different plugs. There's one for water (HU 0), so you can't see it

Answer 136

MTF is a measure of a detector system's ability to render contrast as a function of spatial resolution MTF is used as a metric in spatial resolution in QA and manufacturer spec MTF = 0.1 is generally taken to be limit of detectability of humans although manufacturers often quote an MTF of 0.05 or less in their spec

Answer 137

kVp (decreases kVp increases contrast, but also noise) mAs (increasing mAs decreases noise) Slice thickness (increase slice thickness decreases noise) Window and leveling during analysis

Answer 138

Per TRS-483, needs t be small enough such that volume averaging correction for measured field sizes < 5% Per TG-10, needs to be small enough such that field output is uniform within 1% over detector sensitive volume (much more strict than the TRS-483 definition) This condition is met when Detector width <= FWHM - 2 x rlcpe

Answer 139

Ability of a system to prevent a data transfer error from reaching the patient

Answer 140

First identify potential points of failure and quantify their potential impact using TG 100 workflow Then, weaknesses in the system should be addressed either by eliminating the potential source of error, or where that is not possible, via a robust QA and QC program TG-201 recommendations

Answer 141

QA is a program that ensures that the IT system, and each of its subsystems, is performing according to spec and intent of physicist QC is a process designed to ensure that an individual patient's treatment meets intentions of the physician prescription

Answer 142

* Acceptance testing of each component of the system * Commissioning of each component of the system to assure proper configuration and function within clinical environment * End-to-end testing of data communication along clinical workflow * Annual subsystem QA, often similar to commissioning, to assure that the subsystem was not unintentionally changed since initial commissioning

Answer 143

Two types of QC 1. Automated checksums to ensure data is the same before and after a transfer occurs 2. Human visual checks of data transfer (time outs, weekly chart checks, etc)

Answer 144

Conditions you require are that... 1. Chamber is a reference class chamber as delineated by TG-51 (so must be an ion chamber) 2. Chamber has minimal small field energy spectrum dependence 3. Chamber is small enough to limit volume averaging to less than 5% per TRS 483 or 1% per TG 106 It's very difficult for a chamber to meet all 3 of these conditions. The smallest reference chamber that does meet this condition is the Exradin A26 with a sensitive volume of 4.3 mm3 which may be small enough for 2 x 2 cm2, but not for 0.5 x 0.5 cm2

Answer 145

Daisy chaining does not utilize correction factors and is therefore not recommended by TRS 483, it's simply a multiplication of measurement ratios. The intermediate field method does use correction factors to effectively do... Output factor of small field to intermediate field using SFD x output factor of intermediate field to reference field using reference ion chamber

Answer 146

Because correction factors can be large and somewhat uncertain across the range of field sizes in which reference chambers can be suitable

Answer 147

Sk is the air kerma strength of the source Delta is the dose rate constant expressed per air kerma strength hour GL is the geometry function which accounts for the inverse square law only gL is the radial dose function which accounts for dose fall off due to scattering and attenuation along the transverse axis F is the anisotropy function which accounts for variation in dose with angle relative to transverse plane

Answer 148

Most TPS use the 2D formalism There is no 3D formalism because sources are cylindrically symmetric, meaning rotations along the long axis do not impact dose

Answer 149

Using a WAFAC chamber with seed placed 30 cm from source. The beam passes into the chamber via a8 cm circular aperture. Aluminum filter is placed in aperture to remove low energy photons from source encapsulation. Source is rotated to average out radial asymmetry. Source placed on plastic holder to minimize scatter End result is a seed with a known air kerma strength

Answer 150

Ideally two if you have two available SFD is prone to error, so making two sets of measurements can allow you to cross check your values Most people don't do this though

Answer 151

It's a statement that the ABR requires that all diplomats should abide by to maintain their certification Key points include... * All members should feel valued and respected * Foster a collaborative and inclusive culture * Non-discrimination or harassment * Freedom from harassment * Qualified freedom of speech * Advocate for those who cannot advocate for themselves

Answer 152

To always hold paramount the interests of patients in all circumstances

Answer 153

Code of ethics for AAPM Talks about professionalism, ethics, and authorships/research publication practices

Answer 154

Department of Environmental Protection Radiation Protection Element

Answer 155

First, start with a liquid water phantom. Both calcs should be very close. Tolerance per TG 186 is 2% Then move onto simple heterogeneities Then side by side with actual patients

Answer 156

NOT YET There is not yet enough data relating prescriptions with TG 43 vs model based, and dose to water vs dose to medium calcs TG 186 recommends for now not making the switch until more data is available

Answer 157

New Jersey Department of Environmental Protection Bureau of Environmental radiation

Answer 158

Situation (what happened) Background (context for how the situation may have happened) Assessment (what the potential impact was) Recommendation (what steps can be taken to reduce likelihood of future occurence)

Answer 159

Radiation Oncology Incident Learning System Sponsored by both AAPM and ASTRO

Answer 160

* Incidents (in which an error reaches a patient) * Near misses * Unsafe conditions * Unexpected failures of equipment

Answer 161

* Contribute to a national database and collectively improve the field of radiation oncology. * Track and review internal incidents, near misses and unsafe conditions. * Receive legal protections from discovery afforded by the Patient Safety Act for information that meets necessary requirements. * Receive regular education based on events reported throughout the country, including suggestions on how to prevent errors. * Receive practice-specific reports. * Gain access to analysis tools within the RO-ILS Portal. * Receive regular program education and announcements about features and tools, best practices and general patient safety initiatives. * Learn from RO-ILS user meetings and webinars. * Meet the requirements for up to two Improvement Activities in Medicare's Merit-based Incentive Payment System (MIPS). * Meet the requirement to participate in a PSO within the radiation oncology alternative payment model (i.e., the “RO Model”). * Meet components of accreditation programs, including ASTRO’s APEx® program. * Meet criteria for a practice quality improvement (PQI) toward the purpose of fulfilling requirements in the ABR Maintenance of Certification (MOC) Program. **But the big one is really, provides a tool to help work towards safer and more effective treatments and workflows for your patients and clinic**

Answer 162

dref = 0.6R50 - 0.1

Answer 163

Minimizes dose gradient across sensitive volume of ion chamber

Answer 164

This is a source positioning ruler 1. Device is attached to aferloader transfer tube 2. Dummy cable is extended to a known position, and this position is verified using the in-room camera system 3. The brachytherapy source is then extended to a known position and verified using the in room camera system

Answer 165

+- 1 mm tolerance Done morning before treatments After source replacement/significant repair And ATLEAST quarterly

Answer 166

10 CFR 35 TG 59 (HDR Brachytherapy treatment delivery) TG 56 (code of practice for brachytherapy physics) TG 40 (comprehensive QA for rad onc) TG 41 (remote afterloading technology)

Answer 167

A / B Where A is the dose per MU measured at dmax, with the clinical condition, that is with the cutout in, at the SSD that will be treated, and with the cone that will be used B is the dose per MU at dmax, with a 10 x 10 cm2 open cone at 100 SSD (calibration condition) Note also, same dmax is used. In reality cutout dmax might be slightly different than reference dmax at CAX, but this effect is small An alternative is that you can measure all applicator factors at 100 SSD, and apply a effective SSD inverse square correct in addition to the applicator factor at 100 SSD. **But in practice its easier and more accurate to simply measure the applicator factor at the clinical SSD** Remember: OF = AF x CF

Answer 168

Yes Due to in scattering from the walls of the cutout reaching central axis

Answer 169

Step 1: re-initialize or recalibrate the MLCs in service mode Step 2: retake PF and see if it passes. If not move ontop step 3 Step 3: Call for engineer to inspect and potential replace MLC drive motors

Answer 170

Interlocks MLC leaf edges, allowing leaves to slide relative to neighboring leaves while preventing gaps between the leaves. Used to reduce interleaf leakage

Answer 171

Annually and after repair Whether or not you use it for surveying, it doesn't matter. U still get it calibrated annually

Answer 172

* High deadtimes lead to significant understimates of leakage * GM counters are not able to measure dose * Most GM designs are not able to detect neutrons

Answer 173

Essentially it's all the tests you would perform during a monthly + Radiation profile + X-ray generator function + HU conversion tables + shielding survey + creation of imaging protocols + end-to-end testing

Answer 174

Spatial Integrity

Answer 175

Pretty much the same way you would do it for the entire planning/delivery workflow Take extra care to look for laterality, setup orientation, spatial integrity, and data transfer integrity

Answer 176

Every 6 months (NRC) RSO (NUREG) 3 years (NUREG)

Answer 177

DICOM/DICOM-RT - Standardization of digital imaging information and RT plan related information that can be transmitted, stored, retrieved, printed, processed and dislayed across different vendors Health Level 7 (HL7) - set of international standards for transfer of clinical and administrative data between software applications used by various healthcare providers. Ex. demographic information transfer of Epic to ARIA or Mosaiq TCP/IP - Transmission control protocol/internet protocol, which is a suite of communication protocols used to interconnect network devices

Answer 178

For Co-60, TVL1 = TVLe for concrete, steel and lead For polyenergetic beams, TVL1 > TVLe for concrete, and TVL1 = TVLe for steel and lead For polyenergetic beams, TVL1 in concrete is around 2-4 cm thicker than TVLe For concrete, the increase in compton scattered component dominates primary beam hardening. For Steel and Lead, beam hardening and scatter are approximately equal contributors to increasing TVL1 and TVLe

Answer 179

* Dose rate at dmax of 10ish cGy/min * Energies of 10 - 18 MV for uniformity, however reduced skin dose may be undesirable so 6 MV can also be used * Extended SSD around 4 - 5 meters (also improves uniformity by reducing inverse square law effect) * Gantry at 90 or 270 deg (for pediatrics treated AP, gantry is 0) * Collimator rotation of 45 deg

Answer 180

Desired level is +- 10% of midline dose across body * Some things to help achieve this, * Extended SSDs * If lateral setup, add compensating filters to account for thinner areas (head and feet). Compensating filters should be placed several inches from patient to facilitate some level of skin sparing * AP setup has more uniform body thickness and can be considered if body size geometry allows

Answer 181

Single energy linear accelerator mounted on a robotic arm. Capable of produced a 6FFF photon field for all treatments. System includes an orthogonal kV imaging system with ceiling mounted sources and floor detectors, as well as optical respiratory tracking system which allow for real-time tracking of target position during delivery. X-ray tracking occurs at user defined time increments. Synchrony tracking is realtime using the optical tracking system correlated with the x-ray system to produce model of expected target positioning Treatment delivered using 30 - 300 non-coplanar, non-isocentric beams at various angles of incidence and couch angles

Answer 182

Fixed collimators ranging from 5 -60 mm. these require manual changing during treatment. Also a variable collimator called Iris which can produce 12 discrete field sizes ranging from 5 - 60 mm. These can be switched out automatically during treatment There is also a small MLC called InCise which can produce field sizes up to 115 mm x 100 mm

Answer 183

1 cGy/MU using the 60 mm cone at a depth of 1.5 cm, 80 SAD Vendor recommends using TG-51 protocol, but also provides a physics guide explaining additional recommended steps To find kQ, measure PDD10 at 100 SSD, 60 mm cone. Correct for the PDD for field size and shape (find equivalent square field) to a 10 x 10 cm2 field at PDD(10)x. Correction factor found in literature

Answer 184

Advantages * Extremely small collecting volume, making them well suited for SFD and high dose gradient measurements * Minimall perturb underlying dose distribution, making them advantageous for in-vivo dosimetry * Allow for instantangeous readout * Some MOSFETS also provide a permanent dose record Disadvantages * Finite lifespan of about 100 Gy * Strong temperature dependence * Energy dependence (SiO2 layer is where electron-hole pairs are created during irradiation) * Sensitivity changes with integral dose as trap centers fill (irrevesable)

Answer 185

Metal Oxide Semiconductor Field Effect Transistor

Answer 186

Proportionally As absorbed dose increases, the number of trapped holes increases, and thus threshold voltage also increases

Answer 187

Three leads, the collector, guard and ground separated by an insulating layer. Colelctor and guard are held at the same voltage, meaning there is no leakage from the collector, making triaxial cables ideal for measurement of small charges

Answer 188

Part of the cranial cavity located between the foramen magnum and the tentorium cerebelli

Answer 189

These are applicators for a kV x-ray therapy unit The ends are made of plastic to reduce the amount of electron contamination, while also providing adequate collimation. It also allows easier setup as target area can be directly seen through plastic collimator

Answer 190

* These are filters for a kV x-ray therapy unit * Made out of Aluminum for lower energies and copper for higher energies * They take advantage of the PE to filter out the low energy photons in the spectrum while letting high energy photons pass through. This is useful because the low energy photons increase superficial dose and reduce beam calibration accuracy * The filter material should have a PE absorprtion edge higher than the tube potential, otherwise you get disproprotionately filtering You would not want to use a high Z filter (such as lead or tungsten), because they would be so efficient, that they would have to be built incredibly thin, making them mechanically unstable

Answer 191

Physicist (responsible for technical aspects) Radiation Oncologist (responsible for clinical aspects) Therapists Dosimetrists

Answer 192

General - professional is responsible for training and maintaining competence of the personnel performing a task, and for establishing the procedures and responsibilities. Ex. overseeing daily QA tasks completed by therapists Direct - in addition to general supervision, professional must also be present in the facility and immediately available to provide assistance and direction during performance of task Personal - In addition to direct supervision, professional must be physicall present in room during performance of a task.

Answer 193

Instruments * Multiple SFD detectors * End-to-end phantom * Electrometer * QC device to measure radiation isocentricity Planning and Treatment delivery * Imaging modalities * Immobilization devices * Respiratory and motion management devices * Image fusion and contouring software * TPS that is commissioned for small field calculation and heterogeneity * Treatment machine capable of precise delivery

Answer 194

* Responsibilities * Outlined process for task and parameters (Ex. for simming, slice thicknesses and FOV, for planning, margin selections and calc grid sizes, etc) * Tolerances involved in task * Outlining of expected time intervals * Devices/equipment to be used in process * Imaging to be used along step of process * Checklists at every step of the process

Answer 195

5% of BPE is boron The polythylene has a high hydrogen content, so it's great at thermalizing neutrons Boron has a high absorption cross section for thermal neutrons, so it absorbs them If you had Boron only, it would be much less efficient to slow down then neutrons

Answer 196

1st layer of lead attenuates incident photons and also to some extent reduces energy of fast neutrons, amking the BPE layer more effective BPE thermalizes neutrons and also absorbs them. Emitting neutron capture gamma rays 2nd layer of lead attenuates the neutron capture gamma rays The 1st layer of lead is thicker than the 2nd layer of lead

Answer 197

MLC leaf position offset refers to the difference in position between the MLC setting defined by light field or sensor calibrated to light field, and the radiation field edge (defined by the 50% isodose line). This offset is approximately 0.7 mm for Varian designs DLG models this offset, but is 2x the offset. So typical DLG value is around 1.4 mm. Eclipse assumes leaf tips are square, and the leaf tip itself attenuates the beam down to transmission factor in a single step, instead of a smooth profile (so 100% --> 1% for open field --> MLC leaf tip). DLG is the FWHM of the field with the two leaf tips touching each other (gap of 0). During beam calculation, the MLC positions are cropped away from field by DLG/2 to account for the radiation field being a bit past the physical leaf tip But physical DLG measurement itself is sometimes used as a starting point, and the planning DLG can be adjusted to achieve best agreement with a set of IMRT/VMAT QA measurements

Answer 198

* Measure dose of a reference field (10 x 25 cm2) * Measure dose of the field with bank A blocking, bank B blocking, and average to get a average transmisison factor * Center MLCs over the reference field, and take repeated measurements using different MLC gaps * Subtract MLC transmission from each measurement * Plot corrected measurements (x) and gap size (y) to create a linear fit line * DLG is the x intercept of the extrapolated fit line That is, a theoretical corrected charge of 0 should give the DLG

Answer 199

Validation measurements in commissioning Some errors, particularly in leaf modeling, are more pronounced in modulated lower dose areas. Therefore local normalization would be better at finding these errors

Answer 200

Calculated maximum dose

Answer 201

It's generally less stringent than DTA in high dose gradient regions and dose difference in homogeneous regions It's also less striingent in high noise measurements

Answer 202

CTV, because this includes all gross and microscopic tumor cells The ITV and PTV are usually prescribed the tumorcidal doses however as you need to account for the imperfect dose delivery

Answer 203

Margin >= 2.5S + 0.7R S is the systematic component of error R is the random component of error, may also include internal margin (error accounting for internal movement)

Answer 204

International Commission on Radiation Units and Measurements

Answer 205

Class 1 - 3 Class 1 refers to when radiation lesions are fatal or result in severe morbidity Class 3 refers to when radiation lesiosn are mild, transient, and reversible, or result in no significant morbidity Class 2 is mild

Answer 206

A federally recognized entity that collects information about medical errors and safety risks in a confidential and legally protected environment. The gola being to reduce errors, improve quality and promote safety Ex. includes the PSO used by the ROILS program

Answer 207

Legal protections * Data provided to a PSO is privileged and not subject to subpoena, discovery, or freedom of information act * Data provided to a PSO is also confidential PSO's do NOT provide a legal shield against malpractice or medical errors directly Background: The 2005 Patient Safety and Quality improvement act was created because healthcare providers feared legal liability in the event that medical errors were reported and discvoered. This act allows for aggregation of patient safety data on a national scale, by granting confidential and privileged investigations and reportin gof patient safety events legally to organizations involved in a PSO

Answer 208

Low atomic number materials. Often aluminum

Answer 209

* Increased beam hardening * Increased scatter photon dose and electron contamination (superficial dose) * Decreased dose rate

Answer 210

Increased SSD, decreases the dose per pulse For diodes, this causes a **decrease** in the charge collected per unit dose. This is because charge liberated in the diode may find itself in a recombination center, resulting in electron-hole recombination prior to collection. When dose per pulse is higher, these centers fill quicker, meaning that there are less centers available for recombination and thus less recombination. So a increased SSD, means more available recombination centers relative to pairs produced, which means more recombination, which means reduction in measured charge per unit dose **Note: **this is opposite behavior to ion chambers, where recombination in an ion chamber increases as dose per pulse increases

Answer 211

* Accumulated lifetime dose: accumulated dose produces additional recombination centers, which reduces diode response over time * Temperature: increase in response as temperature increases (0.1 to 0.5%/celsius increase) * Directional dependence: diode design is assymetric which means different amounts of attenuation and buildup vs direction * SSD (dose per pulse) * Energy * Electrometer offset voltage * Field size (changes in scattering conditions)

Answer 212

Electrometer offset voltage refers to the fact that when you set a 0V, there is actually some small voltage being applied still In diodes this can be significant due to their low electrical impendance. Meaning a small offset can cause significant leakage current

Answer 213

Project maximum field size to distance of primary barrier, then add 30 cm on each side

Answer 214

Proton therapy is greatly impacted by changes in patient geometry Multiple plans allow the oncology team to select the most robust plan for the patient's anatomy at time of treatment Ex. a prostate patient may have significant change in rectum filling, which would greatly impact the radiologic path length of a PA field (but not lateral)

Answer 215

Delivering less fields per day reduces treatment time, which is a huge advantage in a proton center where beam availability is limited In proton beams, a single field can produce a uniform target dose (SOBP). In photon therapy, you need multiple fields to produce a uniform target dose. The therapeutic ratio will be greatly impacted in a photon beam if you treated only 1 field per day.

Answer 216

kV targets are angled to reduce self-absorprtion of Bremsstrahlung photons The angle also produces a smaller focal spot, while spreading electron impact area and resultant heat across a wider surface area The anode is also spinning to further increase surface area of heating Drawback: angled target produces a heel effect in which output at the cathode side of the dose distribution is higher than the anode side (approximately 5% higher, but energy and geometry dependent)

Answer 217

* Higher surface dose * Cheaper and require less shielding and staffing than a Linac * More uniform dose distributions for small fields and oblique/irregular surfaces

Answer 218

TG-61 is a formalism for calculating dose to water at surface for a low or medium-energy photon beam. The below equation is the in-air method? * Dose is dose tow ater at a depth of 0 * M is the fully corrected ion chamber reading * Nk is air kerma calibration factor * Bw is backscatter facot which accounts for effects of phantom scatter of a kV x-ray beam when the in-air method is used * Pstem-air is a correction factor accounting for change in photon absorption and scattering between calibration (air) and measurement (air) due to presence of stem At kV energies, kerma is approimately equal to collision kerma (very low Bremsstrahlung production, 0.1%), and thus also dose

Answer 219

NO! * CPE does exist (this is compliant) * Secondary electrons created inside cavity are deposited locally (this is compliant) * All electrons causing ionzations in the cavity arise from the phantom mateiral is NOT true. Most arise from the cavity wall * Secondary electron spectrum is unchanged by presence of cavity is NOT true

Answer 220

Purpose is to relate dose to medium to dose to cavity filly gas Dmed/Dgas = ratio of mass collision stopping powers of medium to gas

Answer 221

1. CPE or TCPE exists 2. All electrons causing ionizations in the cavity arise from phantom material 3. Secondary electron spectrum is unchanged by presence of cavity 4. Energy of secondary electrons created inside cavity are deposited locally Assumptions 2 and 3 imply a need for a small cavity, while assumption 4 requires a larger cavity. These contradict Spencer attix solves condition 4 for small cavities by using restricted mass collision stopping power, which only accounts for secondary electron with energies greater than a cutoff energy. That is, electrons below the cutoff deposit their energy locally, and electrons above are considered in the equation Burlin forumation expands upon spencer attix and generalized for both large and small cavities by eliminating assumptions 2,3, and 4 Typical cutoff energy for restricted mass stopping power ratio is 10 - 20 keV

Answer 222

In a GM counter, townsend avalanches produced a massive amount of ion pairs. The electrons in these ion pairs are collected much quicker than the positive ions, due to the positive ions having a larger mass. Because of this, there is an accumulation of positive charge in the cavity gas which neutralizes the electric field and stops further ionizations from occuring. This continues until the positive ions drift to the cathode and collect an electron, returning to their ground state This process lasts 10 - 100 ms This time is effectively a dead time, since no further counts can be registered

Answer 223

Townsend avalanche refers only tot he cascading **ionizations** caused in **electron** induced ionizations Geiger discharge includes many townsend avalanches and also ionizations caused by UV radiation from excited atoms, which then further cause avalanching

Answer 224

Noble gas - provides chemical stability during repeated ionizations Quench Gas - reduces false signals generated as the ionized fill gas returns to ground state after a discharge An alternative to quench gas is external quenching, where voltage is reduced for a fixed perod following a reading How does a false reading occur? Positive ions after discharge combine with electrons. The difference in energy in this reaction can ionize in the cavity, and if not quenched, can cause avalanching which gives a signal that didn't come from radiation

Answer 225

This is a standard probe geiger counter. There are also pancake probe and modern pocket geiger counters Difference designs have different uses based on wall design. For high energy radiation, the wall is primarily responsible for creation of electrons into the cavity. Low energy radiation can interact directly with cavity. It is **VITAL** to select your GM counter specific to it's intended use. Different wall materials are better at detecting certain types of radiation **Note also:** thickness of wall has no significant impact on response for high energy radiation. This is because, as thickness increases, production also increases, but the probability of electrons reaching the cavity also decreases. These two effects cancel each other out

Answer 226

* Cyclotron * Continuous beam * Monoenergetic (range has to be modulated by energy degraders) * 3.5 - 5 m diameter for protons

Answer 227

* Synchrotron * Pulsed beam (due to time required to cycle magnets) * Energy modulation is possible * 8 - 10 m diameter for protons (25 m for carbon)

Answer 228

Energy degraders made of carbon Nozzle can either container lucite then lead scatterers (double scattering) (scattered beam) or steering magnets (scanning beam)

Answer 229

CT on rails CBCT Out of room CT using a movable but fixed couch Room mounted orthogonal kV x-ray imaging Portal imaging via kV x-ray source mounted along beam path

Answer 230

What to do? * Immediately call service and local engineer for recommendations and for them to come in for repair * Avoid treatment of patients for as long as practically achievable until issue is resolved * Clean up any spill if oil is not hot QA to perform after * Verification of kV and radiation source isocenter coincidence * Verify image quality of CBCT and kV planar imaging * Any other QA engineer may recommend

Answer 231

Varian and IBA They both use cyclotrons Infact almost all proton beam treatments use cyclotrons. Synchrotron is typically a niche

Answer 232

MTF is a quantitative measure of a detector system's ability to render contrast as a function of spatial resolution. The value of MTF is in units of % contrast lost. That is, an MTF of 0.2 means you've lost 80% of contrast. An MTF of 1 means you've lost no contrast MTF is at a maximum 1, and at a minimum used for imaging of 0.1 (10%), but this minimum can be A high MTF indicates that the system is able to resolve a given spatial frequency without too much loss of contrast to distinguish high contrast objects A low MTF indicates that the system loses too much contrast for a given spatial frequency to be able to distinguish high contrast objects

Answer 233

Lithium iodide scintillation detector or boron-trifluoride proportional counter surrounded by a polyethylene sphere The sphere thermalizes incident neutrons These thermal neutrons are then captured in the scintillator, which then emits a scintillation photon. This photon is detected by a proportional counter Using bonner spheres of varying diameters allows you to measure the energy spectrum of the neutron field

Answer 234

Rem ball is a specific type of bonner sphere with a diameter of 10 - 12 inches Rem ball has a response that allows for direct measurement of equivalent dose

Answer 235

For neutron spectrometry, moderated activation foils For general monitoring, bubble detectors, activation foils and other proportional counter designs

Answer 236

Required at vault door Not required elsewhere. It's assumed that concrete shielding that can adequately attenuate a photon beam, will also provide sufficient neutron shielding

Answer 237

The twosource rule treats patient scatter and leakage components of secondary radiation as distinct sources * If patient scatter and leakage transmission factors are approximately equal, shielding thickness may be taken as the larger of the two barrier thicknesses + 1 HVL * If the thickness of each source differs by 1 TVL or more, the larger barrier thickness may be used

Answer 238

Multichannel method Multihannel method allows for correction of a variety of disturbances in the digitized images including... * Nonuniformities in the active coating on the radiochromic film * Minimizes Scanner related artifacts (such as lateral position dependence) * Separate out nondose-dependent abnormalities from the film images It also reduces random noise in the images

Answer 239

the TGTs will likely rest on the patient's skin with this setup, and thus increase skin and midline dose to the patient Some corrective steps would be... 1. Notify doctor of error 2. Place pillow or other spacer between TGT and patient skin during treatment 3. Identify root cause of error and develop procedure to prevent in future

Answer 240

* TGT errors (failure to correct, breaks in tube, unecessary running of tube over patient anatomy, TGT connected into incorrect applicator or channel * Inccorrect source acvitity used to adjust dwell times (wrong date at console) * Damaged applicators * Afterloader retraction failures * Errors in planning

Answer 241

Carina It's cartilage, so it's rigid It shows up well on portal imaging It moves very little with respiration And it can be contoured very accurately during planning It won't show well on a DRR, but it shows very well on a portal image

Answer 242

Varian linacs have a fixed pulse rate (energized accelerating cavity) That is... there are x amount of pulses per second, always What is being modulated is how many of those pulses are electron-loaded by the electron gun The Electron gun is a triode design, in which an electrified "grid" at the end of the gun is used to deflect electrons away from accelerating cavity whenever electron-loaded pulse is not desired

Answer 243

1. Beam at center is harder so is getting attenuated at a lower rate than peripheral 2. More scattering towards central axis than there is away from central axis

Answer 244

1. An initial check of a "rough" calibration 2. Radiation isocenter checks with star shots and/or WL 3. Stability checks (linearity with MU, dose rate, gantry angle, etc) 4. Relative measurements (output factors, wedge factors) 5. Scanning (depth and profiles)

Answer 245

1. Does not provide electron density information 2. Spatial distortions 3. DRR's cannot be generated and correlated with MV or kV imaging on machine 4. More expensive than CTs 5. Longer scan times 6. More staff training 7. Any benefit of MRI can be acquired via fusion from MRI's outside of the department

Answer 246

* T1 has a short TR (time between 90 deg RF pulses) and TE (time between pulse and echo) * T2 has a longer TR and TE * Short TE removes T2 contrast by eliminating time for protons to dephase * Long TR removes T1 contrast * T1 is associated with recovery of long equilibrium magnetization after disturbed by RF pulse * T2 is associated with decay of transverse magnetization after induced by an RF pulse * In T1, the shorter the T1 of a tissue, the higher the signal. Fat appears bright. CSF and water appear dark. White and Grey matter have great contrast * In T2, white matter, and bone are dark. CSF and water are bright. Fat is sometimes bright and sometimes dark, usually bright tho. But fat is not a great indication for deciding between T1 and T2. T2 is excellent for imaging liquid, including edema surrounding tumors

Answer 247

These agents have unpaired electrons, which give rise to a magnetic field 1000x stronger than a proton Paramagnetic molecules strongly influence relaxation rates of nearby protons, which effectively modifies T1 and T2 of water protons

Answer 248

**Scintillation crystal** (converts radiation photons to visible light burst) --> **Photo cathode** (converts visible light burst to photo electrons) --> **Dynodes** (accelerates and amplifies number of photo electrons) --> **Anode** (collects cumulative charge of photo electrons)

Answer 249

Commonly used is NaI[Tl] Relatively high density (3.7 g/cc) Zeff = 45 Highly efficient at capturing diagnostic energy photons by PE Tl doping (0.1%) increases the conversion efficiency of the gamma ray energy

Answer 250

E0 = 2.33 * R50

Answer 251

At near extended distances (up to around 130 cm), the surface dose decreases with increased SSD. This is likely due to removal of low energy head-scattered electrons in the intervening air At large extended distances, such as those used for TSET, surface dose increases as electrons within the primary beam scatter with atoms in the intervening air

Answer 252

Absolute surface dose increases with increased field size Relative surface dose (PDD) decreases with increased field size (dose at dmax increases at a rate faster than the surface dose, hence relative dose decreases)

Answer 253

* dmax becomes shallower * Entire curve shifts shallower * Dmax is larger relative to rest of curve * Rp becomes larger

Answer 254

Due to the randomness of electron paths as they travel through the body At higher energies, they have longer paths, hence more opportunity for their energy spectrum to spread out

Answer 255

True It's best practice to directly measure a cutout's PDD and output However, if you have rectangular field you can approximate PDD in the following way...

Answer 256

GENERALLY increases with increased energy and increased field size But not always true. Just GENERALLY is the case

Answer 257

Electrons are typically employed only for superifical masses, therefore matching at the surface is normally considered adequate regardless of electron+electron or electron+photon

Answer 258

Pt A: prescription dose Pt B: 1/3 of Pt A dose Bladder and rectum doses: < 80% of Pt A

Answer 259

TG-40 * Source location test * Coincidence of dummy and active source * Location of shields if relevant

Answer 260

Where the uterine vessels cross the ureters

Answer 261

A leaking sealed ion chamber would produce incorrect results that may be difficult to detect, whereas a known unsealed ion chamber can have those affects knowingly accounted for If a sealed ion chamber is utilized, care must be taken to ensure that there is no leaking

Answer 262

If there is a reasonable potential for the person to receive 10% or more of **applicable** dose limits (including altered dose limits for minors and pregnant workers) If they will be entering a high or very high radiation area per job description

Answer 263

To determine if the badge was stationary during the entire exposure A distinct grid pattern indicates that the badge was static during the entire exposure, indicating that the badge was likely not being worn at the time

Answer 264

Brief overview of ionizing radiation Dose limits Expected occupational exposure levels, and associated risks Time/Distance/Shielding Concepts of ALARA Source identification Signage Personnel monitoring requirements RSO and Nuc Med contact numbers Patient visitation criteria and rules AND MEDICAL EMERGENCIES SUPERCEDE RADIOLOGICAL CONCERNS

Answer 265

* No minors or pregnant women * Visitors should remaind behidn the 2 mR/hr line on the floor, and visits should be limited to < 1 hr per day * Linens are to remain in the room until surveyed * Ancillary hospital staff should be excluded from the room * Hospital staff that must interact with patient should remain behind shields as practical, and generally follow ALARA principles

Answer 266

Legally, yes this is permitted Licensed physicians are exempted from requirements for transportation of licensed materials so long as they are licensed to possess RAM per 10 CFR 35 or the equivalent state regulation HOWEVER, it is not practically recommended to participate in this sort of practice. Legally it is allowed, but safety wise it is unwise

Answer 267

TG-29 (published in 1986) Khan's textbook

Answer 268

T2 is shown

Answer 269

* Use ultrasound * Use MRI * Identify penile bulb, and on average apex is 3 mm superior of most superior slice of bulb * Use retrograde urethrography

Answer 270

Bone is dark on T1 Relatively bright on T2

Answer 271

TVL of steel (0.11 m) is approx 1/4 that of concrete (0.47 m) TVL of lead (0.056 m) is approx 1/8 of concrete (0.47 m)

Answer 272

Permissible dose in a controlled adjacent Linac room (controlled area) is 5x that of an uncontrolled area (chemotherapy treatment room). Therefore P decreases by a factor of 5 Additionally, the occupancy factor goes from 0.5 to 1.0 So you need one additional TVL of shielding as a result of the change in adjacent room use

Answer 273

* Do you have accurate architectural drawings? * Do you have any dosimetry history on the vault (surveys, badges, etc) * What is currently in the neighboring spaces, do you anticipate any changes? * How does the expected workload differ? * Will additional utilities be necessary? * Where will the new isocenter be in relation to the old isocenter?

Answer 274

This is a cutaway view of a standing wave accelerating waveguide used for a 6X Linac Key features include accelerating cavities, coupled side cavities, the electron gun on the left, and the target on the right The length of each cavity is approximately 5 cm (half the wavelength)

Answer 275

Increase the frequency Ex. Cyberknife utilizes a 9 Ghz X band waveguide instead of a 3 ghz S band waveguide This means the accelerating waveguide is 1/3 the length of a corresponding S band waveguide The downside is that it is harder to keep the waveguide stable at higher frequencies

Answer 276

As field size increases, relative surface dose decreases

Answer 277

CT simulation will give background exposure to staff member (since they're behind barricade that is meant to shield PET component as well as CT component) PET/CT, the approximate exposure is 25 uSv/simulation (about 15 mins at < 50 cm to patient) effective dose equivalent to the staff member

Answer 278

Fundus, Umbilicus, Pubic Symphysis

Answer 279

Scout image only has divergence in the transverse direction DRR has divergence in both transverse and longitudinal direction Take note in the image on the prior page, you see anatoy in the head on different plans overlapping, this is due to the longitudinal divergence. Scout doesn't have that Also DRR utilizes SAD = 100 cm Scout is SAD = approximately 60

Answer 280

* To improve along longitudinal direction, scan with thinner slices * To improve along transverse direction, use smaller FOV (reduces pixel size) CT images are fixed to 512 x 512 resolution, thus a smaller FOV means smaller pixel size

Answer 281

It means the energy of the incident photon is >> than the binding energy of the electron MeV >> keV

Answer 282

Forward for photons Most electrons are scattered at large angles

Answer 283

Backscatter: photon retains 255 keV approximately Sidescatter: photon retains 511 keV approximately These are also the MAXIMUM energies that the photon can retain

Answer 284

Upper wedge < Dynamic Wedge < Lower wedge This is a tricky question actually... * Upper wedges (those we typically use), actually decrease relative surface dose * Dynamic wedges result in very minimal change in relative surface dose until an increase at 60 Wedge angle * Lower mounted wedges (we never use), will increase surface dose

Answer 285

Dynamic wedges - No Physical wedges - Yes, off-axis dose decreases relative to open field. This is because... * Beam hardening * Off-axis beam has to travel longer distance inside the wedge (oblique path)

Answer 286

As field size increases, PDD increases due to increased scatter

Answer 287

Compton mass atten - independent of Z, proportional to electron-density PE mass atten - proportional to Z^3 PP mass atten - proportional to Z

Answer 288

Water and fat are bright Bone is dark

Answer 289

Using either a cotton swab + forceps, or a cutip, or alcohol swab, wipe around the minimum area as denoted by 10 CFR 20 Place the sample in a test tube Measure CPM in an NaI well detector (or using a scintillation detector that's not necessarily a well detector) Convert to dpm by using dpm = cpm/efficiency Compare to regulatory requirements for alpha and non-alpha sources.

Answer 290

Posterior Axillary Boost Used to get coverage to posterior axillary nodes PAB field is typically opposed to the Sclv field

Answer 291

It's pretty controversial topic They're already receiving some dose from tangents, opening up the field further will cover the nodes but also increase dose to lung, heart, and midline Can use electrons, prescribing 90% to a depth of 4 cm treatment (IMCs are a depth of 3 cm) Keep in mind tho, that it is difficult to match the electron AP field with the photon fields. Thus you would expect large hot spots and fibrosis One can also use VMAT for the entirety of the breast treatments. This avoids the match concern

Answer 292

UNSCEAR (UN Scienific Committee on the Effects of Atomic Radiation) BEIR (US appointed committee. Latest report is BEIR VII) They do not make recommends, they only collect and analyze the data. ICRP (international commission on radiation protection) and NCRP (national council on radiation protection and measurements) make the recommendations, that the NRC, DOT, EPA and States may choose to enforce

Answer 293

Magnetron uses pulsed magnetic field Klystron uses constant DC potential

Answer 294

sFOV is the scanning field of view. It's the region completely within the CT fan beam throughout an entire rotation (not just at select angles) Anatomy outside of the sFOV produce artifacts and incomplete image information Number of algoirthms can be used to provide an expanded field of view with some artifact corrections. However, you should keep in mind that these regions are suspect to HU uncertainty, and thus should not be used for dose calculation

Answer 295

They're effectively the same thing CT number is the linear attenuation coefficient rescaled to water HU is the CT number normalized to 1000

Answer 296

This is a child most likely treated for Hodgkin's Lymphoma Blocking is arranged to permit treatment of neck, chest, and underarm lymph nodes, while sparing portion of the lungs to retain respiratory function, and humeral head to minimize impact on bone development

Answer 297

Compton depends almost exclusively on the elctron density, which is proportional to the physical density You can make an approximate estimate on required shielding thicknesses using ratio of physical densities

Answer 298

Internal lasers lack the precision and accuracy required for patient marking and positioning Also external lasers are convenient in that therapists have easier access to mark and align patient, the lasers can be moved and more easily calibrated.

Answer 299

1. Tabletop should be level and orthogonal to the imaging plane (+- 2 mm) 2. Table vertical and longitudinal motional should be accurate and reproducible (+- 2 mm) 3. Table positioning under scan control should be accurate (+- 1 mm) 4. These shoudl be performed with table loaded with at least 150 lbs distributed along patients length

Answer 300

Copper plate for buildup and conversion of photons to electrons Scintillator for conversion of electrons to light photons Amorphous silicon photodiode for conversion of light to electrical signal

Answer 301

Image on the left was kV xrays, imaging on the right was MV xrays

Answer 302

Initially, GM meter to find deficiencies in shielding integrity (gaps, cracks, missing shielding) Then a ion chamber survey meter to measure instantaneous exposures

Answer 303

At home, the seed is no longer under your jurisdiction, and thus the patient should minimize their exposure and just flush the seed In the clinic, some licenses may require that the seed be retrieved and secured for decay in storage, or returned to the manufacturer. Other licenses may permit the flushing of the seed. **When in doubt, retrieve the seed and store in a secure area.**

Answer 304

* If dose rate at 30 cm from a sealed source does not exceed 0.05 mSv/hr * If RAM will only be in the room for < 8 hours, and the RAM is constantly attended and precautions are taken to minimize exposures * Rooms or other areas in hospitals occupied by patients that meet requirements for release from licensee control

Answer 305

Beta minus decay (95.1%) Electron capture (4.9%)

Answer 306

Volume of air/seroma not to exceed 10% of volume of PTV\_Eval

Answer 307

* Authorized user of each type of use permitted by the license * RSO * Nurse * Representative of management who is neither RSO nor AU

Answer 308

* Procedures and procedures * Written directives * Written training records * Reports of misadministrations/recordable events should be discussed and activities to minimize future similar events should be documented * Training program details * Audit reviews

Answer 309

* Annually * At the request of the worker * Whenever NRC notification is required (Ex. overexposure) * Upon termination, repor must be provide to new employer

Answer 310

* Adult with likely potential to receive a dose in excess of 10% of limit * Minor with likely potential to receive a dose in excess of 1 mSv, lens dose of 1.5 mSv, or skin or extremities of 5 mSv * Declared pregnant women who may receive a deep dose equivalent in excess of 1 mSv * Individuals entering a high or very high radiation area These apply for both CEDE and EDE

Answer 311

RSO assigns an estimated exposure to that employee, using the average of a number of the prior month badge readings

Answer 312

* Estimate exposure to the badge * Contact dosimetry lab (Landauer) with the estimate and require a dose correction to the monitoring record (written letter) * Request a new temporary badge to track exposure until next quarter)

Answer 313

**Planned special exposures:** Standard dose limit of a single year, with the cumulative exposures for planned special exposures not to exceed 5x annual dose limit during individual's lifetime **Emergency actions:** There is no limit on exposure per the NRC, however the action must ve voluntary and risks communicated to worker. The EPA **recommends** 250 mSv for life saving response, but again, this is not a requirement.

Answer 314

LET response (under-response for high LET radiations) Energy response below 40 kV Temperature dependence (absorbance increases drastically with increased temperature)

Answer 315

Because the high energy of Ir-192 poses a radiation safety risk to staff during procedure, even if the activity is low

Answer 316

* High leakage relative to measurement * Unexpected Polarity effects * Unexpected Recombination effects * Behavior of response is not well predicted through use of PDD10x to measure kQ for these chambers * More sensitive to irradiation history

Answer 317

1. Wall material (most important) 2. Radius of air cavity 3. Central electrode material 4. Wall thickness (least important) As long as wall material matches a TG-51 detector, the matched data shoild be within 0.5% assuming chamber is "normal"

Answer 318

After every fraction

Answer 319

Tissue inhomogeneity corrections for MV beams

Answer 320

Breast tissue expander

Answer 321

TG 255. This TG report gives an introduction on the imaging modalities, and some advantages and disadvantages to each. PET SPECT MRI Optical Ultrasound You may be surprised to see the bottom 3 on the list. But remember, Molecular Imaging is a field of imaging that focuses on imaging molecules of medical interest within living patients. These molecules are either naturally in the body, or injected. So anything that is selective uptaken within a body and used for imaging counts as molecular imaging. MRI can utilize targeted contrast agents, and can utilize spectroscopic profiles, fMRI and diffusion MRI for diagnoses and imaging of certain pathologies, and also gadolinium contrast to highlight disease. These are all molecule based imaging Ultrasound utilizes microbubbles attached to antibodies, peptides and other ligands that have molecular specificity and are uptaken in certain diseases. Ultrasound as molecular imaging is best used for blood vessel detection and flow mapping, in addition to perfusion studies. Can also be used in angiogenesis studies of tumors Optical imaging utilizes bioluminescents and fluorescent probes to image near infrared for imaging of certain diseases.

Answer 322

TG 111 kV imaging will show energy dependence. So you want a energy independent detector, preferably radcal ion chamber Utilize ACR phantom and measure CTDI as usual Fan and CBCT geometries involve additional considerations as measurement of these differ from one another. Helical vs Axial doses differ due to pitch differences **In general, you don't need to know this TG report well, just know it exists, and have an idea of how CT and CBCT dose is measured**

Answer 323

Primary dose comes from recoil electrons set in motion by photons that scattered for the first time 1st scatter comes from photons that have scattered prior 2nd scattered comes from photons and electrons that scattered from 1st scatter interactions Multiple scatter is as the name entails and is all the remaining dose due to scatter

Answer 324

**IP Address -** Specifies address of specific device/location on network **Port number -** Specifies the process for which the data is to be used / what channel for the data transfer to occur through **AE Title -**Application entity title of the device. it's the destination DICOM application name

Answer 325

A firewall is either a hardware device or a software application that helps protect your network from attackers. The firewall shields your network by acting as a 24/7 filter, scanning the data that attempts to enter your network and preventing anything that looks suspicious from getting through

Answer 326

* Instruct patient to shower and wear clothing they did NOT keep in the isolation room * Survey the patient and all belongings before they are removed from the room * Provide patient with discharge instructions *

Answer 327

Individuals who in the course of their employment, can receive an occupational dose in excess of 1 mSv in any given year

Answer 328

* CTDI is the integrated dose along z axis divided by nominal beam width * CTDI100 is the cumulative dose of a 10cm axial scan, divided by nominal beam width. **For CT, this is measured by a 10 cm long A101 Exradin CT Chamber** * CTDIw is the weighted average of CTDI100 measured at center and peripheral of phantom * CTDIvol normalizes CTDIw by pitch, which relates dose of a helical scan to that of an axial scan * DLP is total energy absorbed by a scanned volume For body phantom (32 cm diameter), 2/3 of weight goes to peripheral CTDI, 1/3 goes to central For head phantom (16 cm diameter), peripheral and central are evenly weighted Both phantoms are 15 cm long

Answer 329

Purely used for thermal insulation. Some high strength HDR seeds can generate enough heat to heat up the active volume of air in the chamber. The styrofoam allows for head localization

Answer 330

Gantry at 0 deg, collimator fully closed, highest energy photon beam

Answer 331

* Dose rate * Roof transmission factor * Height of roof (higher roof, less skyshine) * Lateral distance from isocenter * Solid angle of beam divergence (larger field size divergence means more skyshine since beam goes towards adjacent room more)

Answer 332

Maximum of 180ish uSv/hr or 0.18 mSv/hr for both SEPARATELY McGinley provides this data and also formulas to estimate photon and neutron skyshine. NCRP 151 also provides formulas These formulas can be off by a factor of 10, so always verify with measurement

Answer 333

TG 56 Note also: the NRC gives required QA's that must be done as well. A lot of these are the safety interlock checks that we do, and also the source position accuracy test

Answer 334

LDR: total source strength (or activity) vs prostate volume HDR: total curie seconds vs prostate volume

Answer 335

* For real-time LDR treatment planning, nomogram is useful for estimating the number of seeds that need to be ordered (always order a bit more than what nomogram says to account for needle-induced edema, incorrectly drawn prostate volume on ultrasound, or lost/dropped seeds) * Nomograms are also a useful independent check of the plan you created on the computer * And in the case of a down TPS, they can serve as a simple and dependable backup planning method using various loading techniques (old school LDR)

Answer 336

NO! First off, there is a range of strength for clinical seeds of about 10% variation, which increases as activity increases Additionally, higher-activity seeds will generate a more heterogenous dose distribution (more wasted dose in the form of hot spots around seeds and cold spots in the inter-seed space) Because of this, **higher-activity seeds require a higher total strength.** Yes, less seeds, but still a higher total strength

Answer 337

49 CFR 172

Answer 338

As processor temperature increases, OD increases as rate of reactions also increase This results in a steeper, "faster", film curve

Answer 339

NO! Per ROILS themselves, it cannot be used in a legal case This is because it would discourage institutions from being honest and reporting their incidents if they feared potential legal action

Answer 340

The patient independent part. See red region shown below. This is the head setup that is identical for all patients, so phase space file can be pre-calculated up until then

Answer 341

1. Garbage in = Garbage out: If your input data, which is much more robust for MC, is garbage, the calcs will be off 2. Physicians may need to adjust their prescriptions and dose distribution expectations 3. Follow TG-105 for additional guidelines. It's a good start on implementing MC

Answer 342

2% statistical uncertainty in the Dmax voxel, as recommended by TG-105 Keep in mind, this value is only for the Dmax voxel. You expect out of field voxels to naturally have higher uncertainties

Answer 343

In favor of room-based imaging systems * Simple fixed geometries, less prone to deviation over time * Quicker setup as no robotic arms need to move into position and no gantry needed to move In favor of gantry-based imaging systems * Volumetric imaging can be used to enhance soft tissue rendering * Volumetric imaging can also be used for adaptive radiotherapy and/or dose reconstruction * Can acquire images at more angles and also at the BEV

Answer 344

No kQ values are not provided in TG-51 for parallel plate chambers, due to the uncertainty in wall correction factors in photons beams other than Co-60. Additionally, parallel plate chambers also have a orientation dependence

Answer 345

It's an on and off switch with a gas insulator acting to stop current between cathod and anode. Creatin of plasma cloud when voltage is applied to grid will create a conduction path and act as a switch as long as current flows or anode voltage > 0. Once anode voltage drops to 0, or current stops, thyratron goes back to off state. This is pulsed behavior

Answer 346

Due to heat dissipation needs Alternating electric fields inside the accelerating wave guide are very high power and can generate a lot of heat. To create manageable cooling requirements, we use pulsed beams

Answer 347

Medulloblastoma A cancerous brain tumor that starts near the brainstem in the cerebellum, is fast growing, and can spread to other areas of the brain and cord through CSF. More common in children than adults Most often curative intent CSI is given post gross total resection of tumor at the posterior fossa

Answer 348

Conventional simulation implies the use of a machine capable of the same mechanical movements as treatment units, and same couchtop inserts and immobilization devices. Images can be taken with this simulator with CBCT acquisition, to create a 3D CT scan. It's essentially imaging with something similar to a Linac delivery system CT simulators are CT scanners that are accompanied with special software that allows one to do virtual simulation (in TPS)

Answer 349

1. Safety - survey measurements and CT-dose measurements vs various protocols 2. Electro-mechanical component accuracy 3. Image quality 4. Software and data transfer accuracy 5. Establishment of policies, procedures, and scan protocols Recommendations found in TG-66

Answer 350

The ACR CT accreditation phantom

Answer 351

* Have been trending up in radiation therapy * Involves normal tissue outside of target * Increases risk for secondary cancer * Increases risk for deterministic injury (especially to superficial organs)

Answer 352

1. Assessment - what is estimated total imaging dose 2. Reduction - reduce all unecessary dose (smaller FOV, collimation, less scans in general) 3. Optimization - balance cost and benefit of imaging techniques and frequency

Answer 353

Head Reason being is because smaller diameter anatomy utilizes full-fan beam and full bowtie filter. Larger diameter anatomy has to use half-fan beam with imager shifted and half bowtie filter, due to the limited size of the imager. This reduces dose because each point only gets exposed half as much.

Answer 354

This plot shows the variation of compton cross section per electron/cm2 with energy The top curve is the total cross section of interaction The second curve is the partial cross section relating to transfer of energy to compton scattered photons The bottom curve is the partial cross section relating to transfer of energy to compton recoil electrons **So key takeaway, at lower energies, the photon retains most of its energy during the scatter, at higher energies, the electron gets most of the energy from the photon**

Answer 355

Dose to normal tissue is typically non-uniform. Thus, to plot NTCP curve, you need to use an "effective" dose to represent the dose distribution with a single dose number. There are many ways to define this single dose, the most common being EUD

Answer 356

Proportionality region (around 1000 V)

Answer 357

Neutrons when they interact and are absorbed in the BF3 (boron is specifically Boron-10) or Helium-3 fill gases in a tube at the center of the neutron survey meter, will produce heavy, positive charged products (either alpha particles from BF3 or tritium and proton from He3). These particles as they deposit their energies in the gas volume will also leave a wake of ionized electrons. **Note:** the BF3 and Helium-3 are not used to moderate the neutrons, they are used to absorb the neutrons and create charged particles for collection. To moderate the neutrons, the survey meters ofter utilize polythylene or anything else high in hydrogen

Answer 358

Right outside the vault door This is because all other secondary and primary barriers have enough concrete to sufficiently attenuate the photons, thus they should have no issues whatsoever sufficiently attenuating the neutrons. The door is the only part with no concrete

Answer 359

TRUE The general rule of avg energy = 1/3 max energy is valid only at lower energies This is because average enegry increases slower than max energy increases. At around 18 MV, the rule of thumb is approximately 1/4 instead of 1/3

Answer 360

* Pair production - bound electrons * Compton - "Free" electrons, thus why compton does not depend on atomic number, but instead electron density * Pair Production - Nuclear Coulomb field, hence why it depends on Z^2

Answer 361

TMR = TAR / BSF

Answer 362

End to End testing! You always want to get a measure of the total accuracy of the entire process utilizing the component that was commissioned

Answer 363

It's effectively just an MU calc. The only heterogeneity correction portion is tha tthe depth used for TPR is the effective radiological depth.

Answer 364

The 2D anistropy function is replaced by a 1D anisotropy function which averages out the anisotropy factors at distance r from the source at all theta locations

Answer 365

They do not account for geometrical dose fall off. This is accounted for in the geometry factor, thus factored out of the measured/calculated radial dose function and anisotropy function. That is, if you're in air and the source is not encapsulated, the two functions should = 1 at all locations, since all they account for is source encapsulation, self filtration, absorption and scatter in medium. If there is no medium of encapsulation, they will reduce to 1 at all locations

Answer 366

That the **projection** at isocente rof the MLC leaf end is 5 cm away from the central axis (+5) or 5 cm past the central axis (-5)

Answer 367

Linear Encoding Motors act as linear actuators, by aligning a "T" bold end of a spinning motor with a T-slot in the leaf, with a threaded extender. The spinning action of the motor will extend or retract the leaf based on a clockwise or counter-clockwise spin. The amount of spins determins where the MLC is relative to the calibrated location

Answer 368

1. Patient QA (comparison of MLC position over time vs the planned position over time, can allow for calculation of delivered dose distribution and compare to intended dose distirbution) 2. Speed test 3. Tracking of motor performance over time for maintenance/replacement purposes 4. Retrospective calculation of patient dose in the event of MLC malfunction

Answer 369

1. Head and Neck targets are often large and diffuse, meaning the benefit the bragg peak is diminished as target size increases 2. Head and Neck cancers have large setup and tissue uncertainties throughout the course of treatment (weight loss, shoulder positioning, pitches and rolls across large treatment fields, etc) Maybe in the future when proton-based IMRT because more common place, there may be more of a use for protons in H&N. But as for now, it's not useful

Answer 370

They contain pressurized gas inside of the collection volume. This is a class 2 "Non-flammable Gas" hazardous material. Although these survey meters are exempt from some of the shipping requirements by the DOT, they still must follow some requirements for ground and air shipping such as structural intgerity of shipping, cushioning material, printed labels on package and requirement that **the shipper be registered as a Hazmat shipper, per FedEx and UPS reqyirement.** You must also generate a "Shippers Declaration for Dangerous Goods"

Answer 371

Any employee who is involved in the shipping or receiving of a hazardous material. This includes radioactive material (classification 7), but also pressurized ion chambers (classification 2)

Answer 372

As chamber volume increases, probability of recombination also increases

Answer 373

Scanned proton beams have high instantaneous dose rates, thus you would expect great ion recombination

Answer 374

7 cm This means that signal from the center of a patient, that would travel a combined AP separation of 21 cm, had the uncorrected uptake value decreased by a factor of 8. Thus to correct, you multiply that signal by 8

Answer 375

1. Registration error (even thought the PET and CT components of the PET/CT use the same patient positioning, there can still be a registration error and an error of 2-3 mm is not unusual (especially in lung and any tissue moving over time) 2. CT is scanned with 120 - 140 kVp xrays. PET photons are 511 keV. The difference in energy may introduce error in the attenuation coefficient used to calculate the corrections between the CT calibration curve is based off a lower energy

Answer 376

This, surprisingly enough, is a schematic of a doorless maze That extra corner + having some thicker concrete in between would actually be enough to lower neutron and photon fluence down enough to the point where you wouldn't need a door

Answer 377

Pros 1. Quicker access to patient and machine 2. Cheaper (avoid cost of heavy shielded door) 3. Safer (no chance the door will close on someone) 4. Reliable (shielding works all the time, whether or not you have power. But a door can get stuck) Cons 1. Higher chance that someone can accidentally enter vault during delivery 2. Takes up more space (longer maze, more wind, more floorspace needed) 3. QA on maze safety interlock (laser sensor system would detect if someone passes through and enters the maze and should turn off beam) 4. Noisier (machine noise from inside vault can be heard outside easier)

Answer 378

As field size increases, TVL also increases, due to the increase in scatter

Answer 379

Notice how compton goes up then down

Answer 380

Beam hardening, which increases the average energy of the photon beam, thus decreasing attenuation coefficient and increasing TVL needed BUT, also increase in compton scatter, which decreases the average energy of the beam, thus decreasing the TVL needed. This is true mainly for broad beam conditions however Turns out the 2nd effect actually acts more strongly than the first, so TVLe decreases with depth

Answer 381

They're very close and depend on energy of the beam For higher energy beams, TVL2 > TVL1, this is because beam hardening is greater in this instance. Since PP becomes more prevalent, and PP does not give lower energy compton photons, it doesn't lower the average energy as much as compton would. Additionally, compton scatter is much less dominant in lead in general. As such, beam hardening is slightly more significant than compton reduction of average energy

Answer 382

Curative and breast conservation therapy That is..., lumpectomy + post-operative RT has the same expected local control as a mastectomy So with RT post op, the patient can keep their breast

Answer 383

Calendar days So if event occured on Friday, you still need to inform NRC via phone by Saturday

Answer 384

You are allowed a qualified person to be RSO temporarily up to 60 days until a new RSO is formally appointed and regulatorily approved and put onto the license

Answer 385

At 200 mrem... * Question the therapist about whether a specific event can be identified and subtracted out of the reading * Evluate any recent changes to the employee duties in the past quarter * Contact the badge vendor to request determination of whether the badge exposure was stationary or not * If you cannot find a plausible explanation, consider real-time dosimeter * Document investigation and resolution At 2000 mrem... * Follow all above steps in addition to... * Notify RSO * Provide briefing and/or report to RSC * Survey all work areas accessed by the employee * STRONGLY consider real-time dosimeter

Answer 386

Increases then eventually goes above 1.0 briefly then back down to 1.0

Answer 387

In theory, yes, assuming you apply the correct ISL correction factor. But this is prone to error and more difficult than just directly measuring a new cutout factor

Answer 388

Smaller cutouts have shorter effective SSD (and also bigger divergence) This also means at smaller cutouts will have larger ISL effect

Answer 389

Two methods, 1. Measure cutout factor at 100 SSD, then multiply by ISL using effective SSD at 100 SSD **for cutout** 2. Measure cutout factor at 115 SSD, then multiply by ISLD using effect SSD at 100 SSD **for open field** Lesson: It's too confusing, just directly measure open field at 100 SSD, and cone at 115 SSD and take ratio of charge reading

Answer 390

Trick question, there is no limit

Answer 391

You usually don't This means that HDR shielding is SUPER conservative

Answer 392

Fluke VeriDose Model 37-705 Dual Diodes

Answer 393

What is the approximate order of uncertainty for the following diode dependencies... * **SSD dependence (70 - 130 cm SSD):** +- 2% * **Temperature:** 0.5% per celsius * **Angular (Cylindrical):** < 2% for angles up to 70 deg * **Angular (Non-cylindrical):** can exceed 5% over 40 deg range * **Field Size:** 5% in very large fields

Answer 394

* Consists of three leads, a source, a drain and a gate * Source and drain are connected to a p-type semiconductor * This forms a PNP junction that has a one way flow that can only be overcome by applied voltage * Under the gate is an oxide (insulator) that blocks current flow from source to drain * To run a current, you have to apply a negative voltage that overcomes the threshold voltage * The thresold voltage increases as holes from electron-hole pairs collect at the interface between the oxide and the N substrate and get trapped there * These wholes create positive charge, making it harder for current to flow, thus increasing threshold voltage

Answer 395

1. Energy dependence 2. Temperature dependence 3. Sensitivity change vs accumulated dose (higher dose = more trapped holes = more difficult to add more trapped holes = decreased sensitivity) 4. Angular (depending on design) 5. Time (trapped holes may fade over time)

Answer 396

YES However, it is very impractical to apply Pion values for various dose rates from one patient to the next, and the affect is less significant than the dose per pulse effect. So don't bother

Answer 397

If the instantaneous dose rate is so high that the field strength in the chamber degrades due to the very high ion density, then yes. But in practice this typically doesn't happen and if it did, the general recombination would dominate anyway

Answer 398

Low energy electron beams

Answer 399

True So in theory, you should have a separate Pion and Ppol for different ion chamber + electrometer combos. How much of a difference does that really make though? Likely small

Answer 400

GEC-ESTRO and ABS give the GTV and CTV target definition guidelines, in addition to recommended volumetric doses ICRU gives point based guidelines and definitions of points

Answer 401

Radiograph * Pt A gets prescription * ICRU bladder and rectum points are considered 3D imaging * Pt A can get variable prescription, but try to get coverage while staying within OAR constraints * If MRI available, delineate GTVIR, GTVHR, CTVIR and CTVIR and get coverage to those * OAR doses are D2cc to bladder, rectum and sigmoid

Answer 402

For the first scatter, you use a high atomic scattering foil of uniform thickness in order to spread out the beam For the second scatterer, you use lucite, a low atomic number to help achieve a more uniform beam intensity profile

Answer 403

It's a wheel of rotating thicknesses of plastic that help create the SOBP. It does not scatter the beam, only changes the depth of penetration in the patient in order to achieve the SOBP

Answer 404

Through the use of plastic or wax (low Z) custo molds placed on the patient

Answer 405

* A crystal lattice (LiF for TLDs and Al2O3 for OSLDs) is doped with impurities to create trap centers * There are two bands, valence band and conduction band * When the atoms are irradiated, the electrons will ionize into the conduction band * When they drop back down in energy state, some electrons get trapped inside of trap centers from the impurities in the crystal (depth of trap center relates to energy needed to escape the center) * The energy level of the trap center is somewhere between the conduction band and the valence band * When heat or light is applied to the TLD or OSLD, these trapped electrons get enough energy to leave the trap center, then relax back down to a recombination center/hole trap (also from the impurities), in the process emitting visible light There are also competitive centers, which trap charge carriers but do not contribute to luminescence.

Answer 406

Pencil beam convolution separates the beam into many very small beamlets (pencil beams), and convolves TERMA distribution vs the pencil beam kernel for these small beamlets. Then sums the dose from each beamlet. Neglects modifying dose deposition based on medium density. AAA does pretty much the same thing, the only difference being that it also stretches and shrinks the pencil beam kernel based on local heterogeneities. AAA can stretch the Kernel in 16 different directions Point kernel based algorithms, such as CCC, do nearly the same thing as AAA, the only difference being they look at TERMA at the voxel, how much energy is released within that voxel and not along a beamlet, and are able to stretch and shrink that in more directions than AAA with a finer resolution In the image shown below, AAA would be somewhere between monte carlo and pencil beam

Answer 407

The particles transported through a volume + those absorbed = the source particles into the volume Acuros solves this equation voxel by voxel and throughout the entire CT using a series of partial differential equations and boundary conditions. Way too complicated to memorize

Answer 408

Angle Energy size and location of voxel Also cutoff energy

Answer 409

Because the kernel is described by an equation and function, which describes dose deposition vs angle and effective depth

Answer 410

A pencil beam kernel will approximate interactions over the entire length of the pencil beam Voxel kernels will approximate interactions over the length of the voxel The pencil beam kernel is approximating over a larger volume, and the voxel kernels are smaller and more fine and allow for more fine stretching and shrinking

Answer 411

Electron beams are essentially all scatter Pencil beam ignores side scatters considerably, thereby grossly underestimating dose near central axis (ignores the scatters going towards CAX)

Answer 412

QA is the sum of activities that are designed to ensure that a process meets its quality objectives QC is the sum of activities that are intended to evaluate the performance of a product or a specific device A QA program is much broader, and typically includes QC of specific components used in the process

Answer 413

D90 So 90% of the volume should receive prescription dose The NRC looks at the D90 coverage to decide whether a misadministration has occured or not

Answer 414

Surface/contour irregularities, mainly for MU verification programs that assume cube geometry Otherwise, inhomogeneities is the largest

Answer 415

1. Input beam data needed by the specific program 2. Run through simple geometry cases and compare agreement to TPS 3. Run through clinical situations with increasing complexities and compare agreement to TPS 4. Verify nondosimetric functionality such as import/exporting, data integrity, and treatment unit geometry 5. Establish a routine QA program

Answer 416

ICP uses the TG 45 definitions

Answer 417

Flatness: +- 3.0% for a 30 x 30 cm2 field Symmetry: <= 2%

Answer 418

Pacemaker treats bradycardia (low resting heart rate), by maintaining an adequate heart rate using electrical impulses. Pacemaker can be programmed to maintain certain heart rates ICD treats tachycardia (too fast heart beating) or ventricular fibrillation (chaotic contraction of heart muslces) by shocking (essentially resetting) the heart, similar to how an external defibrillator would work. It's much more violent

Answer 419

1 - 0 1 is the best 0 is the worst 10% is the limiting spatial resolution of a system (or 5% - 20% can be used depending)

Answer 420

Axes are MTF vs Spatial frequency (lp/mm) You measure MTF by imaging a phantom which has high contrast materials at varying distances from one another. These distances and the associated lp/mm are known. You utilize a software that analyzes the line spread function and some other complicated math and calculates MTF vs lp/mm

Answer 421

TCP x (1-NTCP)

Answer 422

It's a process to speed up optimization calculations where a set number of sample points are available to help assess how well dose distribution meets constraints. Volume sampling assigns the points only to structures that have constraints attached to them in the optimizer, thus placing the importance on those constraints

Answer 423

Deterministic is the method that is trying to minimize the cost function at every iteration. This will get you stuck in local minima Stochastic is the same as simulated annealing, in which it allows an increase in the cost function in order to climb out of the local minima

Answer 424

Multiply the air kerma rate constant of the source by the activity of the source on that day and the total treatment time (dwell times + dose transit time) and divide by 100^2 You should expect somewhere from 0.1 - 1 cGy, (approximately 0.2 cGy for APBI), depending of course on the prescription dose. And this is fairly conservative when you consider it doesn't account for patient attenuation

Answer 425

The linear term (alpha) represents lethal damage done by an individual particle track The quadratic (beta) term relates cell death caused by interactions of two particle tracks (multi-hits)

Answer 426

G1 --> S --> G2 --> M --> back to G1 S is the least radiosensitive Late G2 and M are the most radiosensitive Cellular integirty is assessed at checkpoints and cycle is interrupted for repair processes as necessary

Answer 427

OER = dose of radiation to produce effect in ABSENCE of oxygen / dose of radiation to produce effect in PRESENCE of oxygen

Answer 428

Inherent filtration is the construction component of the tube window (usually Silicon (Glass) or Aluminum) Added filtration is typically fabricated from Aluminum or Copper "Unfiltered" part of the spectrum actually includes the inherent filtration

Answer 429

Full fan bowtie and half fan bowtie filters Bowtie filters are used to acquire a CBCT while reducing photon fluence at the periphery where paths are shorter and fewer photons are required for adequate signal, thus reducing unecessary dose to the patient Both are made of Aluminum Additional info: full fan bowties can measure around a 27 cm FOV. Half fan bowties can measure 41 cm FOV. So half-fans are used for larger anatomies

Answer 430

The detector consists of a scintillator (commonly NaI(Ti)) to convert keV x-rays into visible light, which is then detected by an array of photon diodes and converted to electrical signal, which is further converted to digital signal NaI(Ti) has the highest light output efficiency. Bismuth Germanate (BGO) is another possible scintillator material type, which produces 5-10x less visible light signal than NaI(Ti), BUT, it has a higher density and stopping power so you can pack it much smaller, allowing for better spatial resolution

Answer 431

Technically, since they scan multislice, they would be considered cone beam But, the beam is still much more narrow than a CBCT, so you can also argue fan beam? Either way works...

Answer 432

* Measure sinogram data * In software, assign an initial guess of attenuation coefficients for each voxel * Calculate projection for each angle, and compare to the sinogram data * Stochastically adjust your initial guess * Calculate and compare again * Repeat process until good agreement is met between guesses and measurement

Answer 433

Pros * Less noisy (higher SNR) * Can reconstruct with less dose with comparable IQ to filtered back projection * Generally better artifact reduction Cons * More calculation intensive * Can produce false details dependent on seed images

Answer 434

Filtered backprojection

Answer 435

Find the voxel in the measurement set that most closely matches the dose calculated in the treatment plan Then find the distance between those two points This makes DTA really sensitive in low dose gradient regions

Answer 436

For each pixel, it performs both a DTA (sensitive in low dose gradient region) and dose difference (sensitive in high dose gradient region) test If the point passes either one of the two, it's given a pass If it fails both, then it fails The reporting is binary in nature, it either passes or fails

Answer 437

TG 119 (the IMRT QA TG report) introduced the concept 3% / 3mm, 95% pass rate, global normalization

Answer 438

This is a door that is used for Linac vaults with no mazes. We have 3 in our clinic

Answer 439

To reduce weakness, you can either... 1. Increase overlap of the secondary barrier and the door or... 2. Line the secondary barrier with lead and BPE and add a concrete door stop on one side In our clinic we use method 1 + the concrete stop from method 2

Answer 440

EUD is defined as the uniform dose that would generate the same radiobiological effect as the non-uniform dose (delivered over **the same number of fractions**). EUD was originally intended for only the target gEUD extends to both OARs and target In our clinic we have gEUD. The equations are slightly different

Answer 441

At negative infinity, gEUD approaches minimum dose to volume At a = 1, gEUD is the mean dose At infinity, gEUD approaches max dose to volume

Answer 442

1. You need to know the most appropriate value for 'a' 2. gEUD will ignore hotspots for parallel organs, and ignore low and mid doses for serial organs 3. Using gEUD on target can create a very inhomogenous dose distribution 4. You should NOT use gEUD on stereotactic fraction schemes (biological modeling of these schemes is less certain than conventional schemes)

Answer 443

* Wrong jaw size used for SRS Cone patients, overdose of out of field dose * Incorrect small field output factors overdoses * MU calculation errors in general * Stuck MLCs * Incorrect wedge orientations * And of course, the Therac 25 incident (treating in electron mode, but with photon beam current)

Answer 444

IAEA, AAPM and ASTRO

Answer 445

Cumulative (or integral) Differential Cumulative is the most commonly used

Answer 446

Using a check source of known calibrated activity

Answer 447

Two. One pre-implant, one post implant This is to allow for edits made to strategy due to unforseen circumtances arising during the implant procedure

Answer 448

The pubic arch You need to see how narrow the arch is relative to the anterior-lateral sectors of the prostate. The if arch is gonna block off access to portions of the prostate, then they are not a good candidate for brachytherapy

Answer 449

1. Ensure necessary shielding is set up in OR 2. Verbally assist physician with interpreting plan (calling out needle placement coordinates, number of seeds, spacings) 3. Provide recommendations if there is a deviation from plan 4. Track progress of seed deposition (number of seeds inside patient) 5. Confirm all seeds are accounted for at end of procedure while in the OR 6. Conduct OR survey of floor, waste, and linens 7. Survey people as they leave the OR both during and at the end of the case

Answer 450

Take a radiograph of the needles (if the vendor hasn't already)

Answer 451

It's pretty similar to IMRT * It has a transformer (which is similar to IMRT beamlet weighting) * An optimizer (which works to optimize the **similarity metric**) * And a **similarity metric** (Ex. Dice Coefficient, which is used to assess the "goodness" of the registration) DIR is an iterative process and will adjust the DVF multiple times until it finds the best match

Answer 452

In the body, there are expected structures that should not deform that much (Ex. Bone). Regularization acts to prevent over-fitting of these structures by limiting how much the DIR algorithm is allowed to deform them In general, if a voxel has a high attenuation value, it would be considered "less deformable" and more "stiff", meaning the algorithm will not deform it as much.

Answer 453

Pros: * Completing FMEA requires a process to be well-defined and documented * It helps highlight what individual team member's roles are in a process * It helps organize and prioritize points of failure that should be addressed Cons: * It relies on individuals to predict hazards (there may be some hazards that we can't forsee happening) * RPN values can be subjective (should average out multiple people) * Takes a significant amount of time and resources to complete

Answer 454

1. Sum of Squared Differences (minimize average squared intensity differences) 2. Cross Correlation (maximize sum ofproducts of corresponding voxel intensities) 3. **Mutual Information** (the only one suitable for fusion of different modalities)

Answer 455

It pairs voxels of a given intensity in image A with voxels of a corresponding but uniform, (not necessarily similar intensity) in image B. It's able to consider matching voxels of different intensities provided that the shape, size and uniformity of the voxel areas are similar.

Answer 456

Rigid registration - 6 Affine registration - 12 Deformable registration - 3 x N where 'N' is the number of voxels Remember, for DIR each voxel can be translated vertically, longitudinally or laterally independent of one another

Answer 457

**Incident:** An error occured and had an effect on the patient **Near miss:** an error occured but it was caught before reaching the patient **Unsafe conditions:** an error did not occur, but the situation made it more probable than an error would occur

Answer 458

TG 101 This report gives A BUNCH of info, such as dose constraints, immobilization devices and their expected localization accuracy, recommendations on QA, and overall recommendations on things to consider when establishing and SBRT program

Answer 459

Static IMRT

Answer 460

Minimal impact Although they do result in a measureable dose coverage degradation, the affect on estimated TCP is minimal as the prescription levels are sufficiently high that minor dosimetric changes do not impact TCP in a meaningful way. Additionally, dose distributions for PSI are not highly conformal to the target, thus are robust to dose coverage variation

Answer 461

Shape of seed Stranded vs loose Location of implant (closer to veins or urethra or bladder will increase likelihood)

Answer 462

Advantages 1. Relatively simple conceptually 2. Great reproducibility 3. Programmable reproducibility 4. Minimizes respiratory motion Disadvantages 1. Not suited for all patients (intimidating and uncomfortable)

Answer 463

* **Forced shallow breathing (compression)** * **Deep inspiration breath hold (DIBH)** * **Inhale/Exhale scans** * **4D CT for ITV creation** * Active breathing control * Gating (only once while I've been here) * Realtime target tracking

Answer 464

1. Verbal coaching of patient to help uniform it a bit 2. Move the reflector block to a location with more vertical motion (to get a higher amplitude signal for easier peak delineation) 3. Sort through the waveform afterwards and manually select the peaks

Answer 465

A spherical phantom with a central ion chamber at isocenter. Measure charge at an angle that avoids immobilization device, then measure charge at angles that include devices

Answer 466

1. Model device in TPS and insert 2. If no model available, contour device in the plan and include in body 3. Measure ahead of time the impact of device on skin dose and depth dose, and keep this expected uncertainty in the back of your mind 4. Avoid treating through high attenuation regions of the couch/device whereever possible

Answer 467

A cathode with heating filament

Answer 468

It applies a negative potential to the cathode and anode signal with respect to the cathode to cut off current flow. Voltage pulses applied to the grid will essentially eliminate this preventing potential in a pulsed manner.

Answer 469

Tungsten doped with Barium Oxide then coated with Osmium, iridium or Ruthenium * Tungsten has a very high melting point * Barium is an excellent electron donor * Osmoium, Iridium and Ruthenium function to extend the life of the cathode

Answer 470

Maximum Permissible (cumulative annual) Dose Equivalent Same as TEDE essentially

Answer 471

Conceptually, that factor is the fraction of the primary beam dose at 1 meter that is transmitted out of the linac through head shielding By FDA regulation, f <= 0.1%. For shielding calculations, you assume the conservative 0.1% or a factor of 10^-3. Don't go below that unless you can ensure a lower value

Answer 472

Leakage in most places, except near the edges of the primary barrier

Answer 473

False Watch any VMAT plan delivery, they can all vary ganry rotation speed

Answer 474

1. X-ray tube warmup (automatic) 2. Consistency check using system calibration phantom (align phantom using lasers to isocenter, take orthogonal x-rays, ETD measures a shift, shift should be <= 1mm / 1 deg 3. Isocenter check (apply shifts to align phantom to isocenter. Verify that the phantom is properly aligned to isocenter post shifts)

Answer 475

* MLC transmission measurement * Picketfences * MLC spoke shot * Coincidence of light field and x-ray field for all energies * Segmental IMRT (step and shoot) test * Sliding window IMRT at four cardinal angles

Answer 476

MV * Imaging dose * Full range of travel SDD kV * Beam quality/energy measurement vs spec * Imaging dose

Answer 477

This model is called the "multi-target model." It's an older model and has been largely replaced by the linear-quadratic model. Cell survival means that a cell retains its reproductive ability, or in the case of non-proliferating cells (such as nerves, muscles or secretory cells), cell survival is retaining their specific function. 1. 'n' is the extrapolation number and is in theory the number of "targets" that must be hit in each cell to cause multi-hit death. It is also the width of the shoulder. (note: it refers to the shoulder region) 2. 'Dq' is the quasi-threshold dose which defines the width of the shoulder reason and is a measure of the ability for cells to repair damage 3. 'D0' is the final/terminal slope and is the dose at which 63% of cells will die (0.37 cell survival). It is an expression of **radiosensitivity** of a population, and is the slope of the multi-hit kill region 4. '1D0' describes the small initial exponential region slope falling right before the shoulder which is the result of random single hit killing.

Answer 478

A characteristic of the model is that the resulting cell survival curve is continuously bending and there is no final straight portion in log scale. This at very high doses does not coincide with experimental observations At very high doses, the dose-response relationship closely approximates a straight line in a log-inear plot, that is, cell killing is an exponential function of dose. In that sense, the multi-target model actually does a better job of modeling dose response at very high doses

Answer 479

αD is the probability of cell death arising froma single double strande break βD^2 is the probability of cell death arising from multiple "single hits"

Answer 480

Relative biological effectiveness The dose need to cause a biological endpoint for a standard radiation type (x-rays) / the dose needed to cause a biological endpoint for a different radiation type (ex. proton) It's very closely related to radiation weighting factor

Answer 481

Describe the elekta unity MR linacs characteristics in terms of... **Magnet strength: **1.5 T **Energies:** 7 MV FFF **IMRT Delivery type:** Step and shoot **Largest field size:** 22 cm long x 57 cm wide **Bore diameter:** 70 cm bore **SAD:** 143.5 cm **Direction of MLCs:** only in superior/inferior direction (fixed collimator)

Answer 482

In MR linacs, it's an effect that can produce large out of field doses that must be considered in the TPS Highly dependent on angle of treatment surface with respect to magnetic field Electrons backscattered from surface or present in air will scatter away from the field due to magnetic field and deposit significant out of field doses

Answer 483

Secondary electrons created in tissue will spiral back when perturbed by a transverse magnetic field. This is particularly a concern at air-tissue interfaces, the result of which is a high hotspot on the tissue side of the interface. The effect worsens at higher magnetic field strengths To account for it, you need a TPS which models the effect. These are typically monte carlo based modeling. Plan optimization must also account for the effect

Answer 484

It can scan a single sagittal plane at 4 - 16 FPS

Answer 485

Zone 1 - general public access Zone 2 - unscreened patients under MRI personnel supervision Zone 3 - screened patients under MRI personnel supervision Zone 4 - the treatment unit itself The 5 gauss line is the threshold around an MR unit that may produce harmful effects

Answer 486

Iron-fortified foods

Answer 487

Both are measured on varian protocol

Answer 488

You shift the fields to match the patient's daily position. This is done every single treatment, and so the original plan created is almost never actually delivered, it's shifted in some way This is called "Adapt to position (ATP)" After shifting the fields and MLCs, the plan is reclaculated and DVH is evaluated. This works well with 3D plans, but not with IMRT The limitation of this method is that it assumes that the patient's anatomy has not changed at all, and thus the DVH does not reflect internal anatomy change. The contours are the same as they were on the sim CT

Answer 489

Adapt to shape automatically runs a rigid then deformable registration onto the daily MR scan. The contours are deformed and can be manually edited. Because the plan is reclaculated on an MR, electron density values taken from the CT must be applied to the MR via the contours (it will average out the electron densities within a structure. Thus if you have a structure that's part tissue part air, you should contour both parts separately) After contours are carefully checked and edited, you re-optimize It's used post Adapt to Treatment for patients in which there is a change in size or shape of internal anatomy. Or it can be used for stereotactics where anatomical differences are more impactful

Answer 490

Shifts dmax more shallow Decreases %dd(10)x very slightly

Answer 491

Similar formulism, except there's a magnetic field correction factor, kB, which accounts for difference in chamber response due to presence of magnetic field. It's very difficult to measure, so values are Monte Carlo derived Additionally the magnetic field correction factor will be more significantly below 1.000 when chamber is oriented perpendicular to the magnetic field, and will be closer to 1.000 when oriented parallel. Elekta recommends dose should be calibrated with gantry at 90 deg or 270 deg (due to annulus at 0 deg having a helium fill level which can affect the dose output by up to 0.9%). This means you're actually irradiating the side walls of the water phantom, which needs to be accounted for Calibration point is either at dmax (1.3 cm), 5 cm depth (recommended), or 10 cm depth

Answer 492

Mostly non-curative. It's menat to slow disease progression and prolong life

Answer 493

Liver has dual blood supply system (hepatic arties and portal system). Additionally each lobe has it's own independent vasculature supply

Answer 494

Treats GEP-NET (gastroeneteropancreatic neuroendocrine tumors) that are typically slow growing 207 mCi per fraction given once a quarter for an entire year, with 1 month of somatostatin in between and 1 month of rest. The somatostatin slows down hormone release and helps shrink tumor Delivered intravenously 6.73 day half-life

Answer 495

To minimize uptake of Lu-177 in the kidneys

Answer 496

Treats metastatic prostate disease (both soft tissue and bone mets) Around 200 mCi Intravenously 6.73 day half-life

Answer 497

Ra-223 Half-life of 11.4 days Alpha particles 1.5 mCi/kg Treats metastatic castration-resistant prostate cancers (bone mets only)

Answer 498

Physical (more conservative) and effective half-life can vary person-to-person

Answer 499

Preparation room (hot lab) Assay room (hot lab) Administration room (exam room) Storage Waste storage Records must be kept for 3 years

Answer 500

Records must be kept for 3 years Trick second part of question. Lu-177 has a long-lived daughter with a half-life > 120 days. Because of this, it does not qualify for decay in storage per 10 CFR 35

Answer 501

Exposure at surface and 1 meter away Additionally, a surface wipe test of area atleast 300 cm2

Answer 502

* Have corner room if possible * Keep away from infant/children rooms * No pregnant staff allowed to work in room with patient present * Document times of everyone in and out of room to estimate dose * Give training to non-monitored staff ahead of time on radiation safety principles and universal precautions (wear gloves, gowns, show covers) * Restrict visiting times and mark line on floor for visitors to keep distance * Keep everything in room until cleared by physics to throw away out of room * Post RAM signage on room * Use lots of disposable covers in room, around bed, floors, and toilets * After patient gets discharged, perform and document all surveys and wipe tests

Answer 503

Perform a PET scan using dotatate tagged with copper or Gallium-68 to locate somatostatin receptor-positive tumors, which will signify how the compound will be uptaken Based on that PET study, radiologist will make decision if they are good candidate after discussion at tumor boards Blood lab tests are done very frequently, with certain parameters constantly being checked. If they go out of tolerance, patient can't be treated. If approaching tolerance, blood work becomes more frequent

Answer 504

For the first 3 days o Sleep in a separate bed and at least six feet away from anyone else For the first 6 days o Stay at least six feet away from children and pregnant women o Menstruating women should use tampons that can be flushed down toilet o Avoid using disposable items that cannot be flushed down toilet o Sit while urinating and flush toilet three times with lid down o Wash hands often, including after each toilet use o Shower immediately after discharge from the facility and shower daily o Drink plenty of liquids o Use separate towels, washcloths, and toothbrush from rest of household members o Do not share a toilet For the next 6 months o Do not become pregnant or breast feed o Carry around a card to shown to officials anytime you may come in contact with a radiation scanner (such as at the airport)

Answer 505

That something is happening in the MU chambers that decreases the charge collected per unit dose (meaning more dose is needed to get a charge of 1 MU). This can be aging of the electrical components, or a decrease of the sensitive volume mass? Not sure which of the two it is.

Answer 506

Transmission type chambers

Answer 507

Made of aluminum Placed on a shadow tray mounted on the Linac. The shadow tray allowed for drawing of outline of light field projected onto patient at treatment position to highlight borders of low thickness areas. This outline is then given aluminum compensator cutout to compensator for thickness

Answer 508

No! This is because TBI utilizes a much larger field size than the 40 x 40 maximum acquired at commissioning, and also much larger SSDs Additional output factors, off axis ratios, and depth dose data should be measured using a water tank at TBI distances to be used for spreadsheet calculations for TBI

Answer 509

Target (or not) --> Primary collimator --> flattening filter (or not) / scattering foil --> ion chamber --> secondary collimator (jaws) --> MLCs

Answer 510

A transmission type chamber covers the entire beam

Answer 511

AAPM TG 284

Answer 512

IAEA TRS 398 This protocol is very similar to TG-51, the major difference being notations and classification of beam quality specifier (IAEA utilizes TPR20,10 instead of PDD(10)x) IAEA utilizes R50 still for electrons, however they recommend a 20 x 20 cm2 cone instead of 10 x 10 cm2

Answer 513

Proton... don't overthink it

Answer 514

To account for this, the magnetic field is radially altered in the dees in order to time the inject of the proton back to the central region at the time needed

Answer 515

* IAEA 398 * Valid for 50 - 250 MeV protons * Plane parallel or farmer type chambers may be used (plane parallel can be used for all beam qualities, farmer chamber only for certain beam qualities. Many people use plane parallel. PTW bragg peak parallel plate detector are an example of PP chambers made specifically for protons) * Zref is at the middle of the SOBP * 10x10 cm2 field size * Clinical treatment distance SSD * For cylindrical chamber, reference point of measurement is on central axis at center of cavity volume. For plane-parallel it's on the inner surface of the window at its center

Answer 516

1. Measured PDD of SOBP 2. Find practical range (where PDD drops to 10%) 3. Find center of SOBP (Zref) 4. Residual range = Rp - Zref 5. The beam quality is then the effective energy, defined as the energy of amonoenergetic proton beam that has the same residual range measured as that of the given clinical proton beam **Note:** this means that the beam quality is typically very close to the maximum energy in the proton energy spectrum at the reference depth

Answer 517

True Only real difference is how the beam quality is determined But otherwise notations are very similar, there's still a kQ,Q0 like the other two formalisms, it still utilizes chambers with ADCL calibrated dose to water in Co-60

Answer 518

Pencil beam Convolution/Superposition Monte Carlo (not in clinical use due to long calc times)

Answer 519

Energy It's done in the background, different filters have a different proposed imaging source energy which gives various levels of contrasts in the anatomy that's being imaged

Answer 520

Varian uses oil cooling Elekta uses fan cooling

Answer 521

Scattering grid to minimize scatter Scintillation layer to convert incoming kV photons to visible light Amorphous silicon thin film transistor to convert scintillation photons to charge for collection and eventual readout

Answer 522

They can be used as both If paired with a scintillation element (such as with EPID or kVD, it's indirect) If paired with a semiconductor capable of directly converting incoming radiation to charge (such as amorphous selenium), it is a direct detector

Answer 523

EPID images MV photons, this requires copper plate for buildup and conversion of MV photons to electrons, otherwise the detection efficiency would be very low Detection efficiency for kV using indirect method is already good enough, no additional buildup is needed Otherwise the kVD and EPID detectors are almost identical to one another in principle. Both use amorphous silicon TFT and both use Caesium iodide scintillator

Answer 524

Composed of a sensitive area and an electronics area. Charge is collected in the sensitive area and converted through a series of electronics to eventually be used in the digital area. The majority of the available area on the panel belongs to the sensitive area The TFT is an array of transistors in which each pairing of sensitive areas and electronics represents one dexel. It allows for charge storage and eventual readout on a dexel by dexel basis.

Answer 525

Amorphous silicon is a photodiode that converts visible light to electrical signal. It's used in indirect detection and is paired with an scintillator prior and a TFT post (TFT for charge collection and readout) Amorphous selenium is used for direct collection since it's capable of converting incoming x-rays into electron and hole pairs, and by aplying a electric field the charge is collected in the TFT. Even though amorphous selenium has lower z (so low collection efficiency), it can still be built thick to increase signal since the electric field stops the charge collection from laterally spreading

Answer 526

Direct imaging results in the best resolution since you don't get the signal blurring that you get with a scintillator light spreadout However, direct imaging is more expensive In general, mammography utilizes direct imaging since you need to be able to visualize microcalcifications, most other imaging detectors utilize indirect imaging since it's cheaper and gets good enough imaging for their purposes

Answer 527

* Solid state scintillators (typically gadolinium based, but can also be cadmium tungstate) * photodiodes * Substrate Scintillator converts x-rays to visible light, photodiode converts visible light to electrical signal

Answer 528

Committee of publication ethics (COPE)

Answer 529

**American Medical Association** Additional resources: * AAPM Code of ethics * ASTRO * International Committee of Medical Journal Editors (ICMJE) (Research authorship) * American Board of Medical Specialties

Answer 530

Duplicate publication is when the same work is contributed to multiple publishers, or the same publisher multiple times, where there is almost no changes between this publication and a prior publication Ex. If you publish something prior. And now you get more data on the study. You can't just republish it but with updated data, UNLESS the data changes the conclusion of the publication **Why is it unethical?** * Often involves plagiarism (even self plagiarism) * Takes away from redundant resource spending by the publishers * Can result in mis-reporting and confusion of data and number of studies showing something in the field (double counting of data) * The increased number of papers does not reflect additional work or new findings

Answer 531

Neutron production within the body

Answer 532

IMRT has better fall-off at and near the target edge Brachy has better fall-off at distance

Answer 533

False OSLDs yes. But some (not all) TLDs are able to measure neutron doses.

Answer 534

1. Demonstrate energy dependencies (can over-respond by up to 70%) 2. Demonstrate SSD (dose rate) dependencies 3. Demonstrate angular dependencies 4. Demonstrate temperature dependencies

Answer 535

1. Any energy dependencies (issue for diodes, MOSFETs, TLDs and OSLDs) 2. Any dose rate dependencies (issue for diodes) 3. Any issues with low doses (issue for film and ion chambers especially) 4. Angular dependencies (issue for diodes and MOSFETs)

Answer 536

If majority of critical structure is within the 5% isodose line, then the mean dose calculated by the TPS may be reasonably accurate

Answer 537

1. TG-51 2. Measure flatness and symmetry Additional vendor recommended tests 1. Light field alignment 2. Light vs Radiation coincidence 3. Perform MPC for all energies 4. Output vs Gantry rotation

Answer 538

SNC Edge detector

Answer 539

Residency: Standard Imaging Supermax Here: SNC PC Electrometer with a Standard Imaging CDX 2000B

Answer 540

Residency: PTW Advanced Markus, 0.02 cc Here: Exradin A10, 0.05 cc

Answer 541

Residency: Exradin A16, 0.007 cc Here: PTW (pinpoint) N31014, 0.015 cc

Answer 542

Residency: PTW 0.3cc chamber for scanning and reference Here: IBA CC13 for scanning and IBA CC04 for reference

Answer 543

Yes, you don't calc off the scan, however you utilize the scan to get separations and water equivalent depths

Answer 544

* Bi-Lateral (patient sitting up with knees bend and arms to side) * AP/PA * Sweeping Beam * Moving Couch

Answer 545

True 3 of the fields (alternating fields) are treated on one day. The next 3 fields are treated on the next day. And repeat

Answer 546

Where in the room will you treat and what gantry angle gives you best uniformity for your room What is your staffing situation Shielding considerations Is the base the patient stands on rotating or will you do stanford technique? See TG-30 for more recommendations

Answer 547

BF3 gas filled proportional counter He-3 gas filled proportional counter Lithium-Iodide scintillating detector (not as common)

Answer 548

A HAZMAT is a hazardous material shipped good that can cause harm to people or the environment DOT class is a classification of the type of hazardous material being shipped (Ex. Radioactive material is class 7)

Answer 549

State of New Jersey Bureau of Environmental Radiation - Radioactive Material Section This is under the department of environmental protection

Answer 550

Residency: Fluke 451P Here: Victoreen 450

Answer 551

Ludlum Model 3 Pancake probe

Answer 552

University of Wisconsin

Answer 553

**Proportional counter:** the quench gas exists to absorb UV photons, thereby preventing them from creating additional townsend avalanches **Geiger counter:** quench gases exist to supply electrons to the fill gas (stray protons after collection), thereby preventing additional geiger discharges as the fill gas returns to ground state

Answer 554

Typically uses mica window Able to detect x-ray, gamma rays, betas and alphas

Answer 555

Crystal doped with another material, typically NaI:Tl, to detect low energy photons (up to about 360 keV). ZnS to detect alpha particles Tl being thallium Scintillation detectors used in dosimetry are often times plastic scintillation detectors

Answer 556

Thermoplast mask Mold for shoulder positioning Side arm grips at indexable distances for repeatable shoulder depression Neck support for reproducible neck setup

Answer 557

HVAC conduit is usually in the ceiling near the maze, that way it runs as little through the barriers as possible and is away from primary barrier and machine

Answer 558

flattened beams (higher average energy)

Answer 559

Not always, but yes sometimes If it's BID, you treat one field in the morning the other field in the afternoon If not BID, you treat both fields together

Answer 560

The long dashed lines are the raw measurements The solid line is PDI (shifted by 0.5rcav) The short dashes lines is PDD

Answer 561

Any of the following... 1. Wrong patient treated 2. Wrong mode of treatment 3. Wrong treatment site 4. Delivered weekly dose differs by > 30% from prescribed weekly dose 5. Delivered total dose differs by > 20% from total prescribed dose 6. If < 3 Fx, calculated total dose differs by > 10% from total prescribed dose

Answer 562

Any of the following... 1. Wrong patient 2. Wrong radioisotope 3. Wrong treatment site 4. Leaking source 5. Failure to remove sources from temporary implants 6. Delivered dose differs by > 20% of prescribed dose (or 50% in a single fraction)

Answer 563

Any of the following... 1. Wrong patient 2. Wrong treatment site 3. Delivered dose differs by > 10% from prescribed dose

Answer 564

Any of the following... 1. Wrong patient 2. Wrong radiopharmaceutical 3. Wrong route of administration 4. Administered dose differs from prescribed by > 20%

Answer 565

"Recordable Event" Usually the criteria for this are much less than a medical event

Answer 566

Codes of Ethics and professionalism Essentially what responsibilities and guidelines AAPM members and medical physicists as a whole must follow including but not limited to... * Always acting in the best interest of patients * Fostering productive and friendly work environments * Acting only in the realm of their own knowledge and acknowledging limitations of knowledge * Managing conflicts of interest *Always strive to improve individual knowledge, and knowledge of the field as a whole * Adhere to ideals of justice and equality * Strive to provide best quality of patient care and to ensure safety, privacy and confidentiality

Answer 567

Low energy photons: 6 - 10 MV High energy photons: 15 - 18 MV Electrons 1. Adequate build up is necessary to shield contaminate electrons and reduce SSD dependence 2. You don't want TOO MUCH build up, to the point where there is an unacceptable dose shadow below the diode (especially critical if photon diode is used on an electron beam, this can make shadowing up to 20%)

Answer 568

Highest energy 1. Removes contaminant electrons at all energies 2. Ensures better SSD independence 3. Ensure better field size dependence

Answer 569

1. Different transmission thickness to the sensitive zone 2. Change in backscatter from the patient

Answer 570

Increases sensitivity by as much as 5%

Answer 571

* TG-21 uses Nx and Nair * TG-21 can be performed in water, polystyrene, or acrylic * TG-21 uses TPR 20,10 as photon beam specifier * TG-21 uses a calibration depth for photons and electrons beyond dmax, doesn't specify exactly where * TG-21 has A LOT more terms you need to account for due to calibration being allowed in more than just water and also calibration factor being in air * TG-21 is expected to calibrate machine about 1% lower than TG-51

Answer 572

1. high deadtime from pulsed radiation 2. Does not detect neutrons 3. And +- 20% uncertainty

Answer 573

Integrating over a glow curve gives you the total luminescence you should get from your TLD So when you read out the TLDs after irradiation of known dose, you are reading out by heating through the full glow curve which gives you the known luminescence

Answer 574

Ionized Hydrogen gas

Answer 575

Ratio of volume of prescription isodose line to treatment volume

Answer 576

ratio of overlapping volume squared divided by the product of PTV volume and prescription isodose line volume

Answer 577

Ratio of the volumes of the 50% isodose line and the prescription isodose line

Answer 578

Ratio of 50% isodose line volume and PTV volume

Answer 579

Max dose at 2 cm from the PTV

Answer 580

One that... 1. Has a independent algorithm than the TPS 2. Has independent beam input data than the TPS Although it is acceptable to use the same beam data as the TPS, it is generally considered less independent

Answer 581

It's best to try to perform the full workflow, for a few reasons... 1. Dose calc will be more accurate 2. Staff is more familiar with the process than they would be emergency hand calcs that can lead to potential calculation errors 3. The time it takes to figure out an emergency hand calc and recall the workflow for emergency clinical setup treatments may be comparable to just doing everything the usual way Some caveats to keep in mind however include... 1. Can the patient tolerate a CT sim? 2. How rushed exactly is this? The reality in radiation oncology however is that nothing needs to be done within the minute. It's not like the ER where minutes affect patient outcomes. In Rad Onc, the time scales are at the shortest hours, and so you're never too rushed to go the usual route

Answer 582

TG 191 General formalism is similat to TG-51, but with additional LD dependencies First you have the cross calibration factor which is found by the solid water + bolus setup method Then you multiply your corrected reading by taking into account background signal, depletion correction factor, and individual sensitivity correction factors (individual LD response vs average batch response for a given batch) (will require bleaching/annealing afterwards. if you order from landauer, they pre-measure the sensitivites for you). You then multiply by the linearity correction factor (which accounts for change in sensitivity vs irradiation history), the fading correction factor (which accounts for loss in signal due to spontaneous stimulation), beam quality correction factor (that is, the change in response due to beam quality), and an angular correction factor This is the higher accuracy way of doing things, which is what labs like IIROC or IAEA will do. But at most clinics, we do a much more simplified approach.

Answer 583

1. Use the known inherent sensitivity of the individual OSLDs from Landauer (if the OSLDs don't come with pre-measured sensitivity correction, you can just assume 1.000 for them) 2. Establish a calibration curve for a single photon energy by delivering known dose to the OSLDs. Use 6 MV per TG-191 3. Take measurements at different photon energies to see what level of uncertainty that adds to the calibration curve (kQ) 4. Establish a set uniform time between irradiation and readout. Measure readout at different times to establish uncertainty due to timing of readout (kF) 5. You can ignore angular effects, or estimate them using TG 191 6. **Generally, whatever your calibration conditions are, you want to minimize for ksensitivity, kL, kQ, kF, ktheta by minimizing differences in conditions of calibration vs clinical, or by accounting for these uncertainties ahead of time** High efficiency method: 3.5 - 5% 1 sigma, 7 - 10% 2 sigma High accuracy: 1.6 - 3.5% 1 sigma, 3.2 - 6.8% 2 sigma

Answer 584

True Per TG 191, "because bleaching does not fully reset OSLDs to their preirradiated condition, the accumulated dose in OSLDs affects both the sensitivity AND the supralinearity. Because of this, **TG 191 recommends only using OSLDs up to a life-time dose of 10 Gy. Beyond this, there is a measurable uncertainty in sensitivity and supralinearity that is difficult to exactly quantify** TLDs may be annealed indefinitely

Answer 585

As energy decreases, response also decreases for OSLDs and TLDs in electron beams Note: this is contrary to photon fields

Answer 586

High LET beams will cause a saturation and thus under-response of TLDs and OSLDs

Answer 587

Over-respond due to energy dependencies

Answer 588

True This minimizes the "build down" effect that you see out of field and avoids gross over-estimation of dose. The bolus thickness should be similar to the dmax thickness of the nominal beam

Answer 589

* Coincidence of RFP and UCP * Safety interlocks and latching systems * CBCT Precision * Correct dose rates calculated on TDS vs independent calc * Associated MRI QA tests

Answer 590

Isochronous cyclotrons account for relativistic effects by increasing magnetic field strength with radius in order to properly time proton injection back and forth into electric field Varian produces isochronus cyclotrons

Answer 591

Low Z materials, typically plastic or wax

Answer 592

Film is easiest

Answer 593

International atomic energy agency

Answer 594

Where dose drops to 10% past the SOBP

Answer 595

Axial Gamma T1 with contrast 1 mm slice thickness

Answer 596

T1 with contrast

Answer 597

Trick question, you cannot Instead TMR is derived from Monte Carlo

Answer 598

LINACs Cyberknife Helical Tomo (Note: No GammaKnife)

Answer 599

Ray-tracing (TMR10) (more common) Convolution (more accurate) Convolution leads to increased total treatment time by 4-10%

Answer 600

Copper Sulfate

Answer 601

Dual fiber/channel method (one fiber measures signal, one measures background) Chromatic method (two wavelength subtraction method) (Cerenkov has different spectrum than collection spectrum) Time Delay (Cerenkov signal decays quicker than actual signal)

Answer 602

1. Loss of LCPE 2. Partial occlusion of the primary photon source 3. Detector size being too large

Answer 603

Co-60: 3 mm field radius 24 MV: 2.5 cm field radius

Answer 604

True the msr is used for reference dosimetry. If it, itself is a small field, you’re in trouble

Answer 605

Size of square field in which the same amount of phantom scatter is generated as in the non-square field

Answer 606

True For GK, you share a lot of tests as brachy such as… * light indicators * interlocks * timing accuracy * audio visual * dose rate verified with decay calc * Survey meter functionality In addition to some GammaKnife specific tests such as… - UCP and radiation focal spot coincidence - Remote couch movement functionality

Answer 607

Most damaging: Electrons Photons >= 10 MV (due to neutrons) Photons < 10 MV

Answer 608

Trick question There is no one number. Different diodes lose sensitivity at different rates and you should also QA your diodes periodically for sensitivity changes Generic rate might be 1-3% per kGy but greatly depends on models of diodes and on energies

Answer 609

Large increase as temperature increases Approx: 15%/Celsius

Answer 610

1. Post irradiation signal drift (irradiate diode, measure signal change post irradiation and quantify after 1 min) 2. Short term reproducibility (exposure diode 10 times, find standard deviation) 3. Linac dose/MU variation (diodes should have minimal dependence on dose rate set by the Linac) 4. Dose linearity 5. Overall system integrity and cable positioning during readouts

Answer 611

Set diode ontop of solid water at reference condition (we do 10 x 10 cm2, 100 SSD for electrons and 100 SAD for photons), irradiate with 100 MU, correlate the reading to known dose at dmax Now your diodes will exclusively give you Dmax whenever you use them For exit dosimetry (which we do not do in our clinic), the reference point at depth is dmax upstream of the diode. Diode is resting ontop of solid water again, gantry is at 180, deliver field and correlate reading of diode to known dose using MU calculations to find known dose At time of commissioning, you should also quantify the dependencies of the diode vs the calibration conditions listed above. Either apply these dependencies as a correction factor on the in-vivo dosimetry reading whenever patient setup differs from calibration (energy, SSDs, field size, temperature, angle, etc), OR quantify them during commissioning and include in uncertainty budget. These correction factors are as simple as ratios of readings at different conditions factoring in any beam data if necessary (ex. for field size dependence, measuring ratio of readings at different field sizes divided by Scp) (Ex. for SSD dependence, measuring readings at different SSDs but also correcting for ISL). Essentially you want a ratio of charge/dose with dose always being corrected for the change in condition. Or in the case of temperature dependence for example, measuring charge reading for same condition and MU, just at different temperatures

Answer 612

Daily: spot check of system integrity (cables and connectivity) Weekly/Monthly (depending on how often diodes are used): spot check of calibration factor Annual: retake calibration factor and correction factors if applicable. Also re-measure drift and linearity

Answer 613

1. Leakage accumulation throughout treatment 2. Temperature change throughout treatment

Answer 614

None really besides just understanding there is large uncertainty and you're better off using TLDs instead

Answer 615

Both Valley and CTCA are narrow scope A narrow scope license has lower limits on RAM allowed in the facility, in addition to specific uses of said RAMs and specific allowed AUs for each RAM and each allowed usage A broad scope license is typically reserved for large universities and allows for much higher RAM allowed in the facility, in addition to does not specify uses and AUs for specific RAM. There are essentially so many AUs in the facility that it's not worth listing all of them and their individual uses under the license.

Answer 616

Essentially series of documents that provide guidance/clarification/results of research/results of incident investigations/regulatory decisions that can make it easier for you to adopt practices to ensure that your program is NRC compliant

Answer 617

NUREG-1556, Vol 9 This entire procedure must be performed within 3 hours of receiving the package: 1. Wear gloves 2. Visually inspect package for any signs of damage. If damage is noticed, immediately notify RSO before accepting the package 3. Monitor surface of package for any contamination 4. Measure exposure rate at surface and exposure rate 1 meter away and ensure it falls within whatever limits are set by the label 5. Check activity on label and ensure it agrees with what was ordered 6. Open outer package, following any instructions provided by supplier 7. Open inner package, following any instructions provided by supplier 8. Check integrity of the final source container, report any damage to RSO immediately 9. Wipe external surface of final source container and convert CPM to DPM using either liquid scintillator counter (from Columbia), NaI crystal rate meter, or proportional flow counter 9b. External surface wipe test of 300 cm2 should provide a DPM below the limits set by 49 CFR 173 for the type of radiation being emitted 10. Check user request to ensure RAM received was RAM ordered 11. Ensure that receiving this RAM does not exceed allowed license limit 12. Monitor packing material for any contamination before disposing 13. Record receipt, wipe test results and survey results. Keep results for atleast 3 years

Answer 618

Manufacturer --> FedEx --> Us --> FedEx --> Manufacturer Note: we should receive a letter from manufacturer once they receive their source back. We need to maintain records of the letter

Answer 619

* TG - 159 (recommended ethics curricumul for graduate and residency programs) * TG - 249 (Essentials and Guidelines for clinical medical physics residency training programs) * ABR/ACR/RSNA/AAPM/ASTRO/ARR/ARS online modules on ethics and professionalism

Answer 620

NRC FDA DOT EPA

Answer 621

Equipment needed for MR Simulators Safety precautions to take Staffing considerations and time investment of staff QA recommendations Imaging workflows Acceptance and Commissioning recommendations

Answer 622

Spatial integrity and gradient nonlinearity SNR and image intensity uniformity of RF coils RF shielding Informatics/connectivity/data transfer 4D motion verification Emergency stops Patient monitoring system TG 284

Answer 623

TG-284 Mechanical tests * External laser offset from MR isocenter (similar to CT sim) * Table alignment (similar to CT sim) * Table motion accuracy (similar to CT sim) * Indexing accuracy Image quality * Central frequency * Transmitter gain * Flexible RF coil testing * **Geometric accuracy** * High contrast spatial resolution * Low contrast detectability * Artifact evaluation * Percent image uniformity * Percent signal ghosting System check * Room temperature and humidity * Cold head operation * Cryogen level indicator

Answer 624

Increase gradient strength This will also improve chemical shift distortions, megnetic susceptibility and inhomogeneity. It will also decrease slice thickness

Answer 625

* Increasing gradient will decrease the slice thickness * Increasing RF bandwidth will increase slice thickness

Answer 626

It is minimized by a vendor applied 3D GNL distortion correction for each individual MR-SIM protocols That being said, this MINIMIZES the distortion, it does not remove it. So any remaining uncertainty due to distortion must be accounted for in contouring margins

Answer 627

Trick question, there is no TG report Recommended QA is from individual studies. There is no TG report with consensus data YET. Some general good practice QA includes... * The same safety checks that are done for regular Linacs both daily, monthly and annually * Same daily, monthly and annual QA where applicable from Linacs * Additional QA which includes MR image quality assessment, such as distortion classification, SNR, low contrast detectability, high contrast spatial resolution, uniformity, etc * Some additional safety checks for the MR, such as helium level check, emergency power off switches

Answer 628

They're all T2, just taken at different times