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Oncology Specialty Exam 2024 > Radiation objectives > Flashcards

Radiation objectives Flashcards

(103 cards)

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1
Q

What is the primary difference between 2D and 3D radiation therapy planning?

A

2D uses x-ray films and limited CT data, while 3D requires full CT data to accurately represent tumor volumes and organs at risk

3D therapy allows for more precise targeting of tumors and reduces radiation exposure to healthy tissues.

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2
Q

What does GTV stand for in radiation therapy?

A

Gross Tumor Volume

GTV represents the visible or palpable extent of the tumor.

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3
Q

Define CTV in the context of radiation therapy.

A

Clinical Target Volume

CTV includes the GTV plus a margin for subclinical disease spread.

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4
Q

What is the purpose of PTV in radiation treatment planning?

A

Planning Target Volume is designed to account for uncertainties in treatment delivery

PTV ensures the radiation dose is delivered adequately to the CTV.

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5
Q

What is IMRT?

A

Intensity Modulated Radiation Therapy

IMRT modulates the intensity of the radiation beam to conform more precisely to the tumor shape.

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6
Q

What does IGRT stand for and what is its purpose?

A

Image Guided Radiation Therapy; it uses imaging to enhance the accuracy and precision of treatment

IGRT can allow for higher doses of radiation and is useful for moving tumors.

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7
Q

What distinguishes SRS from SBRT?

A

Stereotactic Radiosurgery targets tumors in the brain with high doses of radiation, while Stereotactic Body Radiotherapy treats tumors outside the brain

SBRT typically involves a few treatment sessions, whereas SRS is often a single session.

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8
Q

What is the function of a compensating filter in radiation therapy?

A

Used to limit the primary beam at a specific site

Compensating filters help achieve a more uniform dose distribution.

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9
Q

What is the difference between forward and inverse planning in radiation therapy?

A

Forward planning relies on geometric relationships, while inverse planning focuses on defining target volumes and dose constraints

Inverse planning uses optimization to determine the best treatment plan.

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10
Q

What is a dose volume histogram (DVH)?

A

A cumulative histogram that represents radiation dose received by an organ against its volume

DVHs help assess the acceptability of a treatment plan based on specified constraints.

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11
Q

What are stochastic effects in radiation therapy?

A

Random effects where the probability increases with dose, but severity does not change

Examples include developing a second malignancy.

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12
Q

What does OAR stand for and why is it important?

A

Organs at Risk; they are healthy tissues near the treatment area that could be damaged by radiation

Understanding OARs helps in planning to minimize radiation exposure.

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13
Q

Fill in the blank: In radiation therapy, the term _______ refers to the margin that accounts for uncertainties in treatment delivery.

A

PTV

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14
Q

What is the role of a linear accelerator (Linac) in radiation therapy?

A

Customizes high energy x-rays or electrons to conform to a tumor’s shape

Linacs use microwave technology to accelerate electrons, producing high energy x-rays.

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15
Q

True or False: IMRT typically uses fewer than 10 fixed field beam angles.

A

True

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16
Q

What is the significance of MRI in radiation therapy planning?

A

Enables effective targeting of tumors and delineation of organs at risk

MRI provides excellent soft tissue contrast and avoids radiation exposure.

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17
Q

Define the term ‘isodose’.

A

Relating to points in a medium that receive equal doses of radiation

Isodose distributions are important for planning radiation therapy.

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18
Q

What does the term ‘homogeneity index’ measure?

A

The uniformity of dose distribution in the target volume

A higher homogeneity index indicates better dose distribution.

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19
Q

What is the purpose of a bolus in radiation therapy?

A

To build up the surface dose of radiation

Bolus materials can include rubbery sheets or petroleum jelly strips.

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20
Q

What is the homogeneity index used for?

A

An objective tool to analyze the uniformity of dose distribution in the target volume

It helps in assessing how evenly the radiation dose is distributed across the treatment area.

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21
Q

Define parallel vs serial organ classification.

A

Serial organs: disabling any subunit causes the entire organ to fail (e.g., spine, brainstem). Parallel organs: many or all subunits must be disabled to cause organ failure (e.g., kidney, lungs, liver)

This classification is crucial for understanding the tolerance of different organs to radiation.

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22
Q

What are acute toxicities in radiation therapy?

A

Onset during or shortly after treatment, occurring in rapidly growing tissues, uncomfortable but heal within 3-4 weeks

Examples include skin irritation and mucositis.

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23
Q

What characterizes late toxicities in radiation therapy?

A

Occur more than three months after treatment, can be lasting and irreversible, affect slowly or non-dividing cells (e.g., brain, spinal cord)

These effects can appear years later and may be life-threatening.

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24
Q

What is the primary determinant of late damage in radiation therapy?

A

Fraction size

Larger fraction sizes are more likely to cause late damage, while overall treatment time has little influence.

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25
True or False: Radiation recall is an acute inflammatory reaction triggered by chemotherapy agents after radiation therapy.
True ## Footnote It can occur weeks, months, or years after radiation therapy.
26
What is the significance of the VRTOG scheme?
A guideline for managing radiation therapy side effects ## Footnote It provides a standardized approach to evaluate and treat side effects of radiation.
27
What are the three dominant absorption mechanisms of electromagnetic radiation?
* Photoelectric absorption * Compton effect * Pair production ## Footnote Each mechanism has different dependencies and implications for radiation therapy.
28
What is the difference between x-rays and gamma rays?
X-rays are emitted from processes outside the nucleus, while gamma rays originate inside the nucleus ## Footnote Gamma rays are generally higher in energy and more penetrating than x-rays.
29
What type of radiation is primarily used in most radiation oncology departments?
Electrons ## Footnote Protons are used at a few specialized centers.
30
Fill in the blank: The process of _______ occurs when radiation energy is transformed into a pair of positively charged and negatively charged electrons.
Pair production ## Footnote This occurs at a threshold of 1.02 MeV.
31
What is the Bragg Peak in proton therapy?
The point where proton energy is released, allowing for precise tumor targeting while sparing surrounding tissues ## Footnote This characteristic is one of the advantages of proton therapy.
32
What characterizes early responding tissues in radiation therapy?
They turn over rapidly and have well-defined stem cell populations ## Footnote Examples include intestine, bone marrow, skin, and testes.
33
What is the maximum dose from orthovoltage units?
Found on the surface of patients ## Footnote The depth at which the dose is 50% of the maximum is about 7 cm.
34
What is brachytherapy?
A form of radiation therapy where a sealed radiation source is placed inside or next to the area requiring treatment ## Footnote Often used for prostate cancer.
35
What is the main difference between EBRT and plesiotherapy?
EBRT delivers radiation from outside the body, while plesiotherapy places a source of radiation in contact with the body's surface ## Footnote Plesiotherapy exploits source geometry for treating superficial areas.
36
What type of radiation is Iodine 131 used for?
Injectable radiotherapy, typically for thyroid cancer ## Footnote Patients may remain radioactive for a time after treatment.
37
True or False: Cobalt 60 has been completely replaced by Linac in radiation therapy.
False ## Footnote While Linac has largely replaced it, Cobalt 60 is still used in some settings.
38
What is injectable radiotherapy?
Use of injectable radiotherapy, such as Iodine 131, usually to treat thyroid cancer. ## Footnote Patients may remain radioactive for a period after treatment.
39
What is Cobalt 60 used for?
Medical use of gamma rays from the radioisotope Cobalt 60 to treat conditions such as cancer. ## Footnote It has largely been replaced by Linac due to better energy generation and less radioactive waste.
40
What is the half-life of Cobalt 60?
5.2713 years.
41
What is a Linac?
Primary treatment machine used in modern radiotherapy that uses electricity to generate high energy x-rays. ## Footnote Sophisticated developments have significantly improved its quality and capabilities.
42
What is the skin sparing effect?
Higher energies of radiation cause less absorbed dose to the skin due to electron build up at depths under the skin surface. ## Footnote This effect occurs with megavoltage irradiation.
43
What are the 5 R's of radiotherapy?
Repair, repopulation, reassortment, reoxygenation, radiosensitivity.
44
What does the term 'Repair' refer to in the 5 R's?
Normal tissues can repair sublethal damage from smaller, fractionated doses of radiation while tumor cells accumulate damage.
45
What is 'Repopulation' in the context of radiotherapy?
Radiation can trigger surviving cells to divide faster than they did prior to treatment.
46
In the 5 R's, what does 'Reassortment' mean?
The radiosensitivity of cells depends on their phase in the cell cycle, with cells in mitosis being most sensitive.
47
What is 'Reoxygenation'?
Occurs when well oxygenated, radiosensitive cancer cells die off, allowing reoxygenation of hypoxic areas in tumors.
48
Define 'Radiosensitivity'.
The response of the tumor to irradiation measured by regression extent, rapidity of response, and response durability.
49
What is the Linear Quadratic Model?
Describes the relationship between cell survival and delivered dose, analyzing responses to ionizing radiation.
50
What does the alpha/beta ratio in radiotherapy indicate?
Quantifies the dose response of early and late responding tissues, recognizing two components of cellular damage.
51
What is Biologically Effective Dose (BED)?
A measure of the true biological dose delivered by a combination of dose per fraction and total dose. ## Footnote BED is expressed in terms of different alpha/beta ratios.
52
What does EQD2 stand for?
Equivalent dose delivered in 2 Gy fractions that is biologically equivalent to a total dose.
53
What are Abscopal Effects?
Effects outside the treatment field, which may be positive or negative, likely due to an activated immune response.
54
Define Linear Energy Transfer (LET).
Rate of energy loss along the path of the particle.
55
What does Relative Biological Effectiveness (RBE) measure?
The efficiency of different types of radiation in producing a given biological response.
56
What is the principle of ALARA?
As low as reasonably achievable; a concept in radiation safety to minimize exposure.
57
What are the three components of radiation safety?
* Minimize time near a radioactive source * Maximize distance from the source * Use shielding.
58
What are stochastic effects?
Health effects that occur randomly, with probability of occurrence assumed to be a linear function of dose.
59
What are deterministic effects?
Health effects that vary with the dose, believed to have a threshold, such as erythema and cataracts.
60
What are the effects of radiation on somatic health?
Exposure increases the risk of cancer without resulting in unique cancers not already observed in the population.
61
What is the estimated baseline risk of cancer death?
About 20% in people.
62
What is the threshold for teratogenic effects of radiation?
Estimated to be 0.1 Gy (10 rad).
63
What is the risk of developing leukemia from in utero exposure?
2 to 3 times greater than for an adult.
64
What is the dose of radiation associated with severe mental retardation during fetal development?
1 Gy (10 rad) ## Footnote A reduction of 330 IQ units per 1 Gy is postulated between weeks 8-15 of fetal development.
65
How much greater is the lifetime risk of developing leukemia or other cancers from in utero exposure compared to adults?
2 to 3 times greater ## Footnote This same risk applies for doses in the first decade of life.
66
What is the dose limit to the embryo/fetus of a declared pregnant woman (DPW) during gestation?
500 mrem (0.5 rem) ## Footnote This is 1/10th the annual adult occupational dose limit.
67
What is acute radiation syndrome associated with?
Whole body exposures in a short time ## Footnote Effects may include blood changes, nausea, vomiting, diarrhea, and CNS damage.
68
What is the LD 50 for acute radiation syndrome?
About 400 rad
69
What are the key responsibilities of a Radiation Safety Officer (RSO)?
Responsibilities include: * Researching new and existing radiation regulations * Managing radiation safety programs * Measuring radiation levels * Supervising personnel * Developing radiation handling procedures * Creating departmental budgets * Preparing reports * Auditing safety programs
70
What is the role of a medical physicist in radiation therapy?
Oversees safety, assists with planning treatments, ensures equipment is calibrated, and monitors advanced cancer radiation treatment technologies.
71
What is moist desquamation and how is it managed?
Moist desquamation is a skin reaction that requires prevention of self-trauma with an e-collar.
72
What is the typical timeline for hair regrowth after radiation therapy?
3-6 months ## Footnote Hair may grow back in a different color or texture and in some cases, this change is permanent.
73
What condition can develop in limbs after radiation therapy?
Lymphedema ## Footnote Treatment includes physical therapy and pain medications.
74
What is mucositis and what are its symptoms?
Mucositis is inflammation of the mucus membranes characterized by redness, swelling, ulceration, and thick saliva.
75
What are the common signs of nasal cavity issues after radiation treatment?
Signs include nasal discharge, sneezing, and potential chronic rhinitis.
76
What acute effects can occur in the brain and spinal cord after radiation therapy?
Effects may include neurologic side effects, seizures, and inflammation of normal brain tissue.
77
What is pneumonitis in relation to lung damage from radiation therapy?
Pneumonitis is inflammation of the lungs occurring 2-6 months after treatment.
78
What are the clinical signs of colitis after radiation treatment?
Signs include diarrhea that may contain mucus or blood and increased frequency of defecation.
79
What is the difference between adjuvant and neoadjuvant therapy?
Adjuvant therapy is given after primary therapy, while neoadjuvant therapy is given before.
80
What is the potential late effect of radiation therapy on the esophagus?
Scar tissue formation leading to strictures that may make swallowing difficult.
81
What kind of changes can occur in the eyes due to radiation therapy?
Irritation, decreased tear production leading to KCS, and potential cataract formation.
82
What are possible late effects of radiation therapy on the brain?
Decreased awareness, behavior changes, seizures, or paralysis.
83
What is the common treatment for severe mucositis in pets undergoing radiation therapy?
Temporary feeding tube placement may be necessary if the patient cannot eat.
84
What is the recommended management for patients experiencing lymphedema after radiation therapy?
Physical therapy and pain medications.
85
What is the difference between adjuvant and neoadjuvant therapy?
Adjuvant therapy is extra treatment given after primary therapy, while neoadjuvant therapy is given before primary therapy.
86
What factors influence the decision to use adjuvant or neoadjuvant therapy?
The decision can be multifactorial, including surgical preferences and the need for radiation to shrink tumors.
87
When is radiation often used in an adjuvant setting?
Radiation is often used when margins are not obtained at surgery and the tumor type is not very chemo responsive.
88
What is the therapeutic index in radiation therapy?
The therapeutic index is the ratio of the toxic dose to the therapeutic dose, indicating the safety and efficacy of treatment.
89
What does a higher therapeutic index indicate?
A higher therapeutic index indicates a better chance of a good outcome.
90
What is a radiation boost?
A radiation boost is an additional radiation dose delivered to a reduced field to address potential cancer cells.
91
What is depth dose in radiation therapy?
Depth dose is represented as a percentage of the maximum dose delivered as a function of depth within tissue.
92
What is fractionation in radiation therapy?
Fractionation refers to the number of treatments given, typically 1.8-2.0 Gy per day for six to eight weeks for curative treatments.
93
What is hypofractionated treatment?
Hypofractionated treatment delivers a total dose of 20-35 Gy in fewer sessions, often used for palliative care.
94
What is accelerated hyperfractionation?
Accelerated hyperfractionation speeds up treatment delivery while increasing overall dose, especially for rapidly growing tumors.
95
Define activity in the context of radiophysics.
Activity represents the number of decays a radioisotope undergoes per second, measured in curies or becquerels.
96
What factors affect depth dose distribution?
Depth dose distribution depends on beam energy, depth, field size, distance from source, and beam collimation.
97
What is percent depth dose?
Percent depth dose characterizes the central axis dose by normalizing dose at a depth with respect to a reference depth.
98
What is Dmax in radiation therapy?
Dmax is the maximum dose or peak absorbed dose along the central axis of the radiation beam.
99
What does dosimetry study?
Dosimetry studies the measurement and calculation of radiation doses.
100
What is the role of dosimetrists?
Dosimetrists work with medical physicists in treatment planning, calculating doses, calibrating equipment, and managing the physics section.
101
What is the definition of half-life?
Half-life is the time needed for the activity or number of radioactive atoms to decay to half the initial value.
102
What is half value layer?
Half value layer measures the thickness of absorber material needed to reduce beam intensity by half, usually expressed in mm or cm.
103
Fill in the blank: The typical conventional fractionation for curative courses of radiotherapy is a dose of _______.
1.8-2.0 Gy per day

Oncology Specialty Exam 2024 (7 decks)

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