RAPHEX II Flashcards
(108 cards)
1
Q
does Sr-90 emit beta or gamma?
A
ONLY beta \
Ir-192, Co-60, Cs-137 emit betas but followed by gamma or xrays
2
Q
approximation for Brems production efficiency
A
~ 1 % at diagnostic
-for MV, T* Z *(10^-9)
3
Q
max Brems energy
A
energy of the electron
If this goes on to create characteristic xray, then max characteristic xray has energy of Emax - binding energy
4
Q
the relative mass dnsity of bone is 1.7 times that of water. The relative electron density of bone is expected to be?
A
less than 1.7 times that of water because of high hydrogen content of water
-hydrogen has no neutrons and thus has high electron density
5
Q
HU range for lung, fat, muscle, soft tissue and bone
A
lung- -500
fat- -50 to -100
lung- 40
soft tissue- 100
bone- 1000
6
Q
the effective (or useful) dose rate of a FFF xray beam as compared to a beam with a FF will:
A
decrease with increasing field size
-FFF beams have higher dose rate in center of beam but offaxis they are only slightly higher than filtered beams
7
Q
which beam modality would have greatest % increase in dose rate for a FFF beam as compared to FF beam?
a. 6 MV xrays
b. 15 MV xrays
c. 6 MeV electrons
d. 15 MeV electrons
A
15 MV xrays
Brems increases with energy
-also FF thckness increases with beam energy
8
Q
what is changed for different energy electron beams on linac?
A
magnet current
9
Q
advantages of dynamic wedge vs physical wedge
A
-approx same depth dose as open beam
-field height not limited
-therapists do not have to lift a heavy wedge
-less scatter dose outside field
10
Q
when pairs of abutting AP/PA photon fields are used to cover a treatment area, it is beneficial to have equal collimator settings for both sets of fields because?
A
-eliminates hot and cold spots
-remember it is (match depth * SSD/L1) - (match depth* SSD/L2)
11
Q
what does DICOM RT store?
A
treatment plan info
12
Q
what does DICOM 3D store
A
pixel values and relevant patient info
13
Q
what is in DICOM header file?
A
all patient info, study type etc. but not pixel values
14
Q
An Ir-92 can always be safely installed in which tpe of room without additional shielding?
A
MV linac room
NOT PET because max energy of Ir-192 is 1.1 MeV; PET energy is 0.511 MeV
15
Q
cumulative exposure limit for a lifetime
A
10 mSv * age
16
Q
if a gantry mounted kV xray imager acquires an image while the MV treatment beam is on, the soft tissue contrast in that image would be… comparted to when MV beam is off
A
due to increased scatter, image will be noisier
therefore worse contrast
17
Q
what does indexing the immobilization device do?
A
ensures immobilization device is on same position on couch
18
Q
disadavtange of RF beacons
A
create distortions on MR images
19
Q
can one implanted fiducial say anything about rotation or translation?
A
no because fiducial could have moved… also need pts to define a plane and determine rotation… but if fiducial did not move wrt anatomy, could determine translation only
20
Q
if the edge of an xray field is defined by MLC with rounded leaf ends, the size of the light field used for patient setup wioth be what in comparison to actual xray field size?
A
smaller than actual xray field size because MLCs will let some radiation penetrate through them
21
Q
why are spoliers used to TBI?
A
to increase dose at the surface
22
Q
In SRS, if patient is aligned using only frame coordinate system, it is essential to verify all of the following
except:
-dynamic conformal arcs are used for treatment
-frame pos. has not changed between simulation and tx
-localixzation rods attached to head frame are visible in CT or MR
-treatment room lasers are accurately aligned with linac iso
A
a. dynamic conformal arcs are one of many methods
23
Q
the advantages od treating RSEB using pairs of slightly angled beams instead of a single horizontal beam include all of the following except:
-taller patients can be treated
-reduced xray contamination dose to patient
-more uniform dose distribution
-shorter total tx time
A
-shorter tx time
more Bremss in center of beam (forward directed)- ie more contamination in center
-takes twice as long to treat with 2 beamcs but dose is more uniform
24
Q
dose rate for TBI
A
should be < 0.2 Gy/min to minimize side effects
25
a patient is being simulated for SBRT. What is different about the CTSim process?
SBRT often uses non-coplanar beams, so need to extend sup-inf scan length
26
reasons for sharp dose fall-off in SBRT
-non-coplanar beams
-intermediate beam energy
-small collimator to skin distance
27
main reason for sharp fall-off in gamma knife
-small collimator to skin distance
28
which of the following statements are Ir-192 HDR sources is NOT true?:
1. Ir-192 is beta minus decay
2. Ir-192 eits xrays of several different energies
3.the dose distribution is isotropically symmetric
d. the dose vs distance from the source approximately obeys the IS law for distances < 5 cm
c
dose is anisotropic
also, for d> 5 cm, dose falls off faster than IS due to attenuation
29
how often dose a radiation shielding survey of adjacent areas need to be done for Ir-192 HDR source per NRC
whenever source is changed
30
purpose of using multiple lumans in HDR breast
better dose distribution
31
the fraction of dose delivered during a HDR treatment while source is on transit changes how with activity of the source?
-lower for lower activity source
-transit time is fixed so if source is higher activity then more dose is delivered
32
dose at 20 cm away for 12.7 cGy/s source?
(1/20)^2 * 12.7 cGy7/c
remember that cGy goes with cm and uGy goes with m
33
bakground counts = 400
total counts = 1600
percent standard dev of net counts
sigma = square root (400+1600)
net counts = 1200
percent = 3.7%
34
typical max range of proton therapy beam
30 cm
max energy about 250 MeV
35
do extremities require anti-scatter grids?
no
36
which of the following can be associated with deterministic radiation effects?
1. PET/CT
2. echo cardiography
3. dual energy CT
4. fluoro
5 SPECT/CT
-fluoro
-can get up to 10 Gy at skin which causes radiation burns
37
what does dual energy CT improve?
contrast resolution
38
tube current of fluoro vs radiography
fluoro is 1/100 of radiography
39
residence time in nuc med
1.44 * initial activity * effective half life
-include % uptake in initial activity; for example, 40% uptake in thyroid is 0.4 uCi/uCi administered
40
treshold energy for photodisintegration
10 MeV
41
a bi-exponential function when plotted on a semi-log graph looks like what?
2 straight line segments
42
which of the following statements regarding DAP is incorrect?
1 it is independent of distance from xray tube
2. it is highest dose to any portion of the patient's skin during the procedure
3. it is the total amt of energy imparted to a patient during a procedure'
4. it is typically measured at surface of xray tube port
2 is wrong- this is peak skin dose
DAP is independent of distance because IS cancels out with area
43
change in Z, A, and N, with positron decay
A positron is a positively charged electron, having an elementary electric charge of +1. Simply stated, it is produced within the nucleus by the conversion of a proton to a neutron and a positron, with the emission of the positron produced from the nucleus. Positron decay thus reduces the atomic number by 1 to Z–1, increases the neutron number by 1 to N+1, and leaves the mass number A unchanged, as positrons (and ordinary negative electrons) have a negligibly small mass compared to those of neutrons and protons.
44
ROC curve stuff
Sensitivity = TP / (TP + FN)
Specificity = TN / (TN + FP)
Positive predictive value (PPV) = TP / (TP + FP)
Negative predictive value (NPV) = TN / (TN + FN)
accuracy is area under ROC curve
45
the radiation weighing factor is a simplified version of what?
the RBE
46
The parameter that provides the best estimate of skin radiation dose during a fluoroscopy procedure is _
A. the displayed kerma area product B. the displayed dose at the interventional reference point C. the total fluoroscopic time used for the study D. the total number of DSA frames used for the study E. both A and B
B. the displayed dose at the interventional reference point The displayed air kerma (AK) is defined at a point 15 cm below isocenter at the interventional reference point (IRP). However, to accurately calculate skin dose, correction factors must be applied for the distance from the patient’s skin entrance to the IRP position, attenuation of the x-rays caused by the table pad, angulation of the x-ray tube, etc. In general, and without proper correction factors, the displayed AK will overestimate skin dose if there is gantry motion during the procedure. The same kerma-area product (KAP) can be delivered using a lower dose and a larger field of view, or a higher dose and a smaller field of view.
47
residual activity in nuclear medicine
activity that remains in flasks or syringe (not all of it is injected into patient)
48
excess of protons aligned parrallel vs anti-parralell 3T MRI
0.001%
49
accuracy of diagnostic test
The accuracy of a diagnostic test equals (TP + TN) / (TP + FP + TN + FN). Note that the denominator is simply the total number of all subjects. In this example, the accuracy equals (420 + 340) / (420 + 45 + 340 + 40) = 0.90
50
what happens to Z, N in beta minus decay
the neutron-to-proton (N/Z) ratio decreases from parent to daughter In beta-minus decay, a neutron is converted to a proton plus a negative electron, with the emission of the electron as a beta-minus particle. As a result, the neutron number of the decaying nucleus decreases from N to N–1, and the atomic number increases from Z to Z+1, so that the neutron-to-proton ratio decreases from N/Z to N–1 / Z+1. Beta particles are emitted with a range, or spectrum, of energies from near-zero to a maximum, or end-point, energy characteristic of the particular radionuclide. Since the atomic numbers of the parent and daughter are different (Z and Z+1, respectively), they are nuclides of different elements and, therefore, have different chemical properties. A transition energy Q of at least 1.022 MeV is required for positron (beta-plus) but not negatron (beta-minus) decay. Following beta-minus decay (as well as other forms of decay), emission of characteristic atomic radiations commonly, but not always, occurs.
51
dose from tomosynthesis vs mammo
they are comparable
52
The axial resolution in ultrasound imaging can best be improved by using...?
a shorter pulse length Higher frequencies yield shorter pulse length and, thus, improved axial resolution
53
Which of the following reconstruction options would improve visibility of low-contrast structures in a chest CT scan?
A. use of a lung filter B. use of a bone filter C. use of a soft-tissue filter D. reconstructed of thinner transverse slices
use of a soft-tissue filter Lungs and bone filters are sharpening filters designed to enhance spatial resolution; these will increase image noise, however, and thus degrade low-contrast resolution. Reconstruction of thinner slices will result in fewer counts per reconstructed voxel and, thus, also increase noise and degrade low-contrast resolution. Soft-tissue filters, on the other hand, are low-pass filters that effectively suppress noise in the reconstructed images, but with some loss of spatial resolution.
54
Which of the following is not a contributing factor to average glandular dose in a mammogram? A. x-ray tube target material B. x-ray tube focal spot size C. x-ray tube voltage D. x-ray beam half-value layer (HVL) E. degree of breast compression
focal spot size
55
Which of the following will improve low-contrast resolution in a radiographic image? A. Change the anti-scatter grid from a grid ratio of 10:1 to one with a grid ratio of 8:1. B. Move the patient closer to the image receptor. C. Reduce x-ray tube current. D. Use a smaller field of view. E. Increase the x-ray tube voltage.
use smaller FOV
will reduce scatter
56
Which of the following modalities employs a storage phosphor to capture the x-ray signal? A. indirect digital radiography B. direct digital radiography C. computed radiography D. film-screen radiography E. xeroradiography
CR
57
In Doppler ultrasound, which of the following angles is considered the maximum angle between the Doppler beam line and the direction of blood flow for which acceptably accurate measurements of blood velocity can be obtained? A. 12 degrees B. 30 degrees C. 60 degrees D. 70 degrees E. 84 degrees
Note that the Doppler shift is proportional to cosθ and, thus, increases as the angle θ decreases, reaching a maximum for θ = 0 degrees (flow directly towards or directly away from the transducer) and decreasing to 0 (i.e., no measurable Doppler shift) for θ = 90 degrees. An angle of θ = 60 degrees is considered the maximum angle at which the Doppler shift can be reliably measured
58
The American College of Radiology (ACR) SPECT phantom is able to assess three features of image quality. What are they?
contrast, resolution, uniformity
59
A patient is scheduled for an FDG PET scan, but the technologist discovers the patient received 185 MBq (5 mCi) of 131I just 24 hours earlier. The technologist calls you for guidance as to whether the FDG PET scan should proceed. A. The FDG study may be performed because the 131I emissions are singles that have a negligible impact on the coincidence detection of the 18F scan at the low (185-MBq) 131I activity.
ANSWER
B. There is a problem because 131I emits some coincidence 511-keV photons. C. There is a problem because 131I emits high-energy photons that would interfere with the coincidence detection of 18F annihilation gamma-rays.
D. The procedure should not be performed because the total radiation dose to the patient from the two diagnostic scans would be unacceptably high.
E. The FDG scan is not recommended because the FDG uptake might perturb the radioiodine distribution.
A. The FDG study may be performed because the 131I emissions are singles that have a negligible impact on the coincidence detection of the 18F scan at the low (185-MBq) 131I activity.
60
what is a laminar flow hood
A laminar flow hood is a cabinet with an air-flow system designed to minimize the possibility of air-borne radioactive materials escaping from the hood and contaminating the radiopharmacy and the radiopharmacists. The air-flow system directs radioactive particulates or gases into a filter trap. A laminar flow hood is not otherwise sealed, however
61
Which of the following performance measurements is not required as part of the acceptance testing of a dose calibrator? A. sensitivity B. geometry C. linearity D. constancy E. accuracy
Sensitivity (i.e., the measured signal per unit activity) is not a clinically relevant measure of dose calibrator performance.
62
One of the commonly used features in radiomics that describes the “peakedness” of an image attribute is illustrated graphically below. This feature is called positive if the distribution is narrower than a normal distribution and negative if broader than a normal distribution. What is the name of this radiomics metric?
excess kurdosis
63
n MRI, flow void is more likely to occur for _____. A. T1-weighted images in the presence of slow blood flow B. T1-weighted images in the presence of fast blood flow C. T2-weighted images in the presence of slow blood flow D. T2-weighted images in the presence of fast blood flow
One of the commonly used features in radiomics that describes the “peakedness” of an image attribute is illustrated graphically below. This feature is called positive if the distribution is narrower than a normal distribution and negative if broader than a normal distribution. What is the name of this radiomics metric?
64
PET outperforms SPECT in each of the following except _____. A. sensitivity B. energy resolution C. spatial resolution D. count-rate performance E. overall image quali
energy resolution The energy resolution of lutetium yttrium orthosilicate (LYSO), the most commonly used scintillation detector in current PET systems, is 16% to 20%. The energy resolution of thallium-doped sodium iodide, the scintillator detector used in gamma cameras, is considerably better, only 8% to 10%.
65
The MR images depict the prostate gland in a patient with prostate cancer. The image in the left panel is T2-weighted, and the image in the right panel is heavily diffusion-weighted. The arrow identifies a tumor. Choose the answer which makes the following statement correct. The tumor appears bright in the diffusion-weighted image because _____. A. water is able to move more freely in the tumor than in the surrounding glandular tissue B. water has a greater T2 value than surrounding glandular tissue C. fat in the tumor appears bright in the diffusion-weighted image D. water motion is more restricted in the tumor than in the surrounding glandular tissu
water motion is more restricted in the tumor than in the surrounding glandular tissue Diffusion-weighting causes reduced signal in regions where water diffuses more freely. The tumor has a higher signal because water does not diffuse as freely in the tumor as in the surrounding glandular tissue.
66
starburst artifact comes from where?
collimator septal penetration
67
The units for luminance and illuminance are _____
cd/m2 and lux
68
The GSDF is related to _____
diagnostic display monitors The abbreviation “GSDF” stands for “Grayscale Standard Display Function” and is a characteristic of display monitors. It is usually measured with a specific set of patterns featuring a series of gray-level steps.
69
CT scans produced with a mobile C-arm fluoroscopy unit are most suitable for _____. A. examinations following orthopedic surgery B. breast examinations C. abdominal surgery follow-up D. cardiac examination with contrast material E. lung cancer screening
examinations following orthopedic surgery CT slices produced with a mobile C-arm have poor low-contrast performance and exhibit pronounced motion blurring since each scan takes several seconds. Therefore, the most appropriate use would be for imaging following orthopedic surgery, since the objects of interest have high contrast and can be immobilized to eliminate motion
70
The CTDIw for an adult head CT series is 60 mGy, the pitch is 0.5, and the scan length is 18 cm. The dose length product (DLP) for this examination is, therefore, _____.
2160 mGy-cm The dose-length product (DLP) is equal to the CTDIvol times the scan length. The CTDIvol is equal to the CTDIw divided by the pitch. Therefore, DLP = (60 mGy/0.5) (18 cm) = 2,160 mGy-cm.
71
The purpose of synthetic mammograms produced by digital breast tomosynthesis (DBT) units is to _____
provide the radiologist with a 2D mammogram with no additional radiation dose to the patient Some digital breast tomosynthesis (DBT) units combine the information from the tomographic slices to produce conventional-looking mammograms for the radiologist at no additional dose to the patient.
72
Which of the following radiographic techniques will lead to the greatest patient entrance dose? A. 80 kV, 200 mA, 0.4 s B. 80 kV, 300 mA, 0.2 s C. 100 kV, 100 mA, 0.04 s D. 100 kV, 25 mA, 1.0 s E. 140 kV, 80 mA, 0.01 s
80 kV, 200 mA, 0.4 s The patient entrance dose is proportional to the product of the square of the kV, and the mA times the exposure time. Combination A gives the largest value: 512,000
73
In ultrasound, the impedance of the quarter-wave matching layer is _____.
the geometric mean of the impedances of the PZT and the skin
74
Many ultrasound scanners employ speckle-reduction algorithms in the image processing chain. Speckle in ultrasound is caused by _____.
interference among echoes from scatterer
75
With respect to the figure below, medium 1 is fat, medium 2 muscle, and the angle of incidence for beam X is θ = 20 degrees. Which of the following is the correct angle of refraction?
Based on Snell’s law, sin(incident angle) / sin(transmitted angle) = c(medium 1) / c(medium 2) where c is the speed of the wave. Since c(fat) = 1,450 m/s and c(muscle) = 1,580 m/s, the angle of refraction as the wave passes from medium 1 (fat) into medium 2 (muscle) must be larger than the incident angle θ.
76
The spatial average, time average intensity in an ultrasound beam is _____. A. proportional to the ultrasound frequency B. proportional to the transducer surface area C. inversely proportional to the transducer surface area D. proportional to the acoustic power of the beam E. inversely proportional to the impedance of soft tissue
proportional to the acoustic power of the beam Intensity, by definition, is the rate at which energy passes through a unit area. The time average intensity is equal to the power in a wave divided by the area over which the power is dispersed, with units watts/m2. Of course, for the ultrasound system, other intensity descriptors, such as the pulse average intensity, result in significantly greater values than the time average intensity.
77
Which of the following is not a goal associated with the new full-field digital mammography (FFDM) phantom designed with the American College of Radiation (ACR) to test FFDM system performance?
to test contrast ratio in contrast-enhanced digital mammography (CEDM) According to the website https://www.sunnuclear.com/shopgammex/mammo-ffdm-phantom, the new mammo FFDM phantom:
“Evaluates artifacts over the entire detector with a single image. Measures and monitors FFDM systems' signal to noise, resolution and image quality. Simulates radiographic characteristics of compressed breast tissue. Eliminates backscatter and provides quick detection of objects from 0.14 to 1.0 mm.”
The new phantom is not designed for CED
78
the diameter of the unfocused, single-element transducer is 15 mm. What is the approximate length of the near field produced by a transducer operating at 5 MHz and a transmitting waves that propagate at 1,540 m/sec through tissue?
18 cm The length of the near field for a given transducer is defined as d2 / 4 × lambda, where lambda is the wavelength of the beam.
79
Which of the following is not a contrast agent? A. Gd-DTPA B. iodine-127 C. protein-shelled microbubbles D. carbon dioxide E. PTCA
PTCA Gd-DTPA is used for MRI, iodine-127 (the stable isotope of iodine) for CT, protein-shelled microbubbles for ultrasound, and carbon dioxide DSA. The abbreviation “PTCA” stands for “percutaneous transluminal coronary angioplasty.”
80
The maximum permitted exposure rate during cine fluoroscopy is _____
not applicable Section 21 CFR 1020.32 Fluoroscopic equipment provides the framework for regulatory requirements. Sub-section 1020.32(f) recognizes that there is a difference between regular fluoroscopy and cine fluoroscopy. 1020.32(d) establishes limits only for fluoroscopy, and there is no exposure rate limit specified for cine fluoroscopy.
81
US angle of divergence in far field
sin(theta) = 1.22 * lambd/d
d is transducer diameter
82
equation for reflection at US boundary b
(difference of impedance/sum of impedance)^2
83
Two transmit focal zones were used for the image in the figure below. Increasing the number of transmit focal zones will have which effect on the resolution of the object shown?
improved lateral resolution, poorer temporal resolution Increasing the number of transmit focal zones will increase the lateral resolution over the image. Each additional focal zone that is added will require a separate excitation of the array for each transmit focal distance. However, the finite pulse transit time in tissue limits the transmit pulse repetition frequency. Because of this, and because subsequent processing is needed for each of the multiple focal zones being resolved, temporal resolution will suffer as this process will take more time to complete per frame, thus decreasing the total frame rate.
84
Decreasing the depth setting for a 2D ultrasound acquisition has which effect on the frame rate if all else is kept equal?
A. It increases the frame rate. B. It decreases the frame rate. C. The frame rate remains the same. D. There is not enough information provided to answer the question.
increase
Decreasing the depth setting using a given transducer will generally increase the frame rate. The reduction of image depth will decrease the amount of time it takes to acquire pulse-echo data for each beam line, so for a fixed number of “A” lines the frame rate will increase.
85
A region of the body which includes boundaries 0.7 mm apart in the axial direction is imaged with an ultrasound transducer operating with a spatial pulse length of 1 mm. Which of the following should be done in order to resolve the boundaries?
Nothing needs to be done; the region will be resolved. Axial resolution is equal to one-half of the spatial pulse length (SPL), as illustrated in the figure below. Therefore, any boundaries that are separated by a distance greater than one-half the SPL will prevent pulse overlap and, thus, be resolved. In this question, the boundaries are separated by 0.7 mm in the axial direction, and one-half the SPL is 0.5 mm given that the SPL is 1 mm. Since the boundary separation is greater than one-half the SPL, the boundaries will be resolved.
86
What is the one-way intensity half-value thickness for a 4-MHz ultrasound beam (assuming a soft-tissue attenuation coefficient of 0.5 dB/cm/MHz)? A. 0.50 cm B. 0.75 cm C. 1.0 cm D. 1.5 cm E. 2.0 cm
1.5 cm
The intensity half-value thickness (HVT) is defined as the thickness of material that will reduce the initial ultrasound beam intensity by half. Relative intensity is a log-based calculation defined as 10 log(I2/I1) where I1 and I2 are the comparative intensities of the incident and the returning echoes of the beam. Solving this equation for a relative intensity that is decreased by one-half will yield a result of a 3-dB reduction. Thus, any half-value thickness will reduce the ultrasound beam by 3 dB. This can then be used in the relationship HVT(cm) = 3 dB / [attenuation coefficient (dB/cm)] or in terms of frequency, HVT (cm) = 3 dB / [(0.5dB/cm) /MHz × f(MHz)]. Solving this for the given values yields 1.5 cm
87
Which of the following tests is not required by the ACR as part of the annual quality assurance program of an ultrasound system? A. physical and mechanical inspection B. image uniformity C. system sensitivity D. electronic image display performance E. geometric accuracy
geometric accuracy Physical and mechanical inspection, image uniformity, system sensitivity, and electronic image display performance are required quality assurance tests that must be performed annually for ACR-accredited ultrasound units. All other specified test are optional.
88
Which of the following tissue boundary interfaces result in the least amount of intensity reflection? A. liver-kidney B. muscle-bone C. fat-muscle D. muscle-lung E. bone-lung
liver-kidney Intensity reflection at a boundary is determined by the acoustic impedance (Z) of the two boundaries at any given interface. The larger the difference in the acoustic impedance between two mediums, the larger the intensity reflection of the ultrasound beam. As indicated in the table below of pressure and reflection coefficients for various interfaces, the liver-kidney boundary has the smallest difference in acoustic impedance between the tissues and will have the least amount of intensity reflection.
89
Which of the following statements is correct?
The average latency period of radiation-induced leukemia is about five years. Based on the Hiroshima and Nagasaki A-bomb survivor data, the average latency period for radiation-induced leukemia is about five years. The biological effectiveness of alpha particles will not change with dose fractionation. With acute radiation exposure, the higher the dose, the shorter the prodromal syndrome. The higher the LET of a radiation, the lower the oxygen enhancement ratio (OER). Finally, radiation does not produce new, unique mutations, but merely increases the incidence of spontaneously occurring types of mutations.
90
Which of the following statements is correct? A. Radiation-induced cancer has no defined threshold dose. B. In general, cells that rarely divide are the most radiosensitive. C. An individual exposed to a whole-body absorbed dose of ~6 Gy dose of gamma-rays experiences the hematopoietic syndrome as well as the gastrointestinal syndrome. D. Among the Japanese A-bomb survivors, there is no evidence of an increase in GI cancer.
Radiation-induced cancer has no defined threshold dose. Although controversial, radiation-induced cancer does not appear to have a definite threshold dose. In general, cells that rarely divide are the most radioresistant. The dose for gastrointestinal toxicity in humans is estimated to be 10–12 Gy. Among the Japanese A-bomb survivors, an increased incidence of GI tumors—including liver, stomach, colon, and esophageal tumors—has been demonstrated
91
A radiation worker received whole body irradiation composed of 25 mGy of x-rays plus 0.2 mGy of 10-MeV heavy ions, and 10 mGy of 10-MeV protons, resulting in total effective dose of _____.
49 mSv The total effective dose received by the radiation worker is 25 mGy × 1 (weighing factor, wr, for x-rays) + 0.2 mGy × 20 (weighing factor, wr, for heavy ions) + 10 mGy × 2 (weighing factor, wr, for protons) = 25 + 4 + 20 = 49 mSv. The fact that this was a whole-body irradiation means that all organs received the same absorbed dose
92
At which of the following gestational ages is the threshold dose the lowest for induction of mental retardation due to irradiation in utero?
8 to 15 weeks
In utero irradiation at sufficient doses can cause mental retardation, with sensitivity for this effect being greatest at a gestational age of 8 to 15 weeks. Radiation induction of mental retardation is a deterministic effect, the threshold for which is not exceeded in diagnostic imaging studies.
93
Which of the following is not a governmental organization regulating various aspects of the medical uses of radioactive materials?
NCRP
The NCRP (National Council on Radiation Protection and Measurements) is an authoritative advisory (non-governmental) organization whose mission is “to support radiation protection by providing independent scientific analysis, information, and recommendations that represent the consensus of leading scientists.” The FDA (Food and Drug Administration), DOT (Department of Transportation), and NRC (Nuclear Regulatory Commission) are governmental agencies that regulate various aspects of the medical use of radioactive materials; the latter two agencies also regulate various aspects of non-medical uses of such materials.
94
Radiation induces chromosomal changes in peripheral blood lymphocytes. The minimum dose that can be detected by measuring dicentric chromosome is _____.
0.25 Gy Radiation can induce a variety of chromosomal abnormalities in mammalian cells, including dicentric chromosomes that can be detected in peripheral blood lymphocytes after doses as low as ~0.25 Gy (or 25 cGy).
95
The reference-point air kerma recorded during fluoroscopically guided interventional procedures refers to the air kerma accumulated at which of the following points
15 cm from isocenter toward x-ray tube The International Electrotechnical Commission (IEC) defines the interventional reference point to be 15 cm from the isocenter of gantry toward the x-ray tube. This is supposed to be a location representative of the patient’s skin. The FDA has separate reference points for measuring dose when testing a fluoroscopic unit. For units with the x-ray tube under the table (GI units), the exposure rate is measured at 1 cm above the table top, and for c-arm units the exposure rate is measured 30 cm in front of the detector.
96
Radiation-induced cancer is an issue of concern for the general public. The National Council on Radiation Protection and Measurements (NCRP) estimates that the fatal-cancer risk per sievert is about _____.
5%
According to the National Council on Radiation Protection and Measurements (NCRP), the lifetime cancer risk estimate is about 5% (or 0.05) per sievert.
97
A busy female interventional radiologist routinely wears both a personal dosimeter on her collar above the lead apron and a second dosimeter on her torso beneath the apron. Her average annual dose readings over the past five years have been 80 mSv to the collar badge and 4 mSv to the body (torso) badge. She declares that she is three months pregnant. Based on current National Council on Radiation Protection and Measurement (NCRP) recommendations, she _____.
may maintain her current procedure volume Current National Council on Radiation Protection and Measurements (NCRP) recommendations limit fetal exposure to 0.5 mSv per month. The radiologist’s body badge provides a preliminary estimate of expected fetal dose. The badge’s reading of 4 mSv per year is equivalent to 0.33 mSv per month. This is two thirds of the guidance limit.
98
The regulatory effective dose limit for a patient undergoing an interventional radiologic procedure for a biliary drain is _____
not limited
99
The current estimated population average annual medical radiation exposure in the United States is _____.
medical only is 3 mSv
total with everything else is 6 mSv
100
When designing shielding of a diagnostic imaging suite, what is the shielding design goal in terms of dose in an adjacent controlled area? A. 50 mGy in any week B. 15 mGy in a year C. 0.1 mGy in any week D. 0.02 mGy in any hour E. unrestricted (i.e., no limit)
0.1 mGy in any week National Council on Radiation Protection and Measurements (NCRP) Report No. 147 recommends a shielding design goal (in air kerma) of 0.1 mGy per week for controlled area
I guess 20 uSv/h is not a design goal but just a condition to meet
101
Diagnostic medical imaging examinations of a pregnant woman subject an embryo or fetus to doses in which of the following ranges?
0–10 mGy According to National Council on Radiation Protection and Measurements (NCRP) Report 174, Table 3.2, most diagnostic medical imaging examinations subject the embryo or fetus to doses of less than 10 mGy. Exceptions to this may be prolonged fluoroscopic procedures (including fluoroscopically guided interventional procedures), CT examinations (especially multiphase) of the abdomen and pelvis, and several nuclear medicine studies (e.g., myocardial-perfusion study, PET).
102
How long should nursing mothers be advised to interrupt breast-feeding following administration of iodine-131
permanently for the current baby following administration Guidance on precautions for lactating mothers who receive radioactive material can be found in the Nuclear Regulatory Commission (NRC) NUREG-1556, Appendix U, and in the International Commission on Radiological Protection Publication 128, Table D.1. Although there are currently no universally recognized guidelines, recommended lengths of time nursing
mothers should be advised to interrupt breast feeding include the following: 24 hours for 99mTc radiopharmaceuticals; 12 to 24 hours for 18F radiopharmaceuticals or 68Ga radiopharmaceuticals; 7 days for 111In-white blood cells or 123I radiopharmaceuticals; 14–28 days for 201Tl-chloride, 67Ga-citrate, or 89Zr radiopharmaceuticals; and permanently for the currently nursing baby for 131I or 124I radiopharmaceuticals.
103
Which cells/tissues in the below list are considered the most radiosensitive?
bone marrow cells Radiosensitivity is the relative susceptibility of cells, tissues, organs, etc. to the injurious action of radiation. In general, it has been found that cell radiosensitivity is directly related to the rate of cell division and inversely related to the degree of cell differentiation. This means that actively dividing, relatively undifferentiated cells are at greatest risk of damage by radiation. As such, bone marrow cells have the highest radiosensitivity among those listed.
wr= 0.12
104
Among the civilian population most heavily exposed as a result of the Chernobyl nuclear reactor accident, the most significant radiation effect was _____.
an increase in the incidence of thyroid cancer The most significant radiation effect of the Chernobyl nuclear reactor accident was a significant increase in the incidence of thyroid cancer, most notably among children. This was attributed to the radiation dose to the thyroid delivered by iodine-131, which was released to the environment in large amounts and picked up by people in milk, drinking water, etc.
105
The curie (Ci) is a unit of activity based on the activity of 1 gram of _____, with 1 Ci equal to 37 _____.
radium; GBq The curie is a conventional (i.e., non-System Internationale (SI)) unit of activity based on the activity in 1 gram of radium; it corresponds to 3.7 × 1010 disintegrations per second (dps). The SI unit is the becquerel (Bq), which is defined as an activity of 1 dps. Therefore, 1 Ci = 3.7 × 1010 Bq = 37 ×x 109 Bq = 37 GBq
106
A nurse stands 1 meter from a patient undergoing an interventional procedure. The entrance skin dose rate for the patient is 35 mGy/minute. With no shielding in place, the scatter radiation level where the nurse is standing is approximately _____.
0.035 mGy/minute The x-rays produced by the fluoroscope will scatter off of the patient in all directions. The scatter radiation at a meter is approximately 0.1% of the incident exposure rate. In the scenario, the DAP meter showed 35 mGy/min, making the scatter radiation at one meter 35 mGy/min × 0.001 = 0.035 mGy/min in the nurse’s position.
107
Which of the following is not a primary benefit of adding filtration to a fluoroscopic x-ray beam?
increased high-contrast spatial resolution Adding filtration to the x-ray beam eliminates lower-energy scatter that wouldn’t normally reach the detector. This will harden the x-ray beam and lower the patient’s entrance skin dose. While this does lower the dose, increasing the x-ray beam’s penetration can decrease subject contrast due to less absorption in the patient.
108
Assuming the automatic exposure control (AEC) is in operation, all of the following increase the radiation dose to the patient’s skin, as well as to the surrounding staff, except _____. A. increasing the tube potential B. increasing the tube current C. increasing the patient size D. increasing the magnification E. increasing the frame rate
ncreasing the tube potential Increasing the tube potential will increase the penetration of the x-rays passing through the patient’s skin. This will, in turn, lower the total skin dose and the dose to the surrounding staff because there will be less scatter at the surface of the patient and less absorption. Likewise, with the automatic exposure rate control engaged, the mA will generally be lowered to preserve the baseline image quality, thus ultimately decreasing the dose to the patient’s skin
