MEDICAL DOSIMETRIST CERTIFICATION BOARD PRACTICE TESTS
Density of healthy lung tissue
Approximately 1.00 g/cc
Accelerator component for electron injection
Electron gun injects electrons into the linear accelerator
Time post-fertilization for severe birth defects
13 - 24 weeks
Decay constant for a 60-day half-life source
0.662
Function of a maze in a treatment room
Minimize radiation levels at the door
Anatomic location of seminal vesicles
Inferior to the prostate, angled posteriorly near the rectum
Missed treatment days due to LINAC malfunction
May be compensated by adding fractions with weekend treatment if possible
Lowest dose delivery to femoral heads in 4-field box technique
100 source-to-axis distance (SAD), equal target dose to all fields
Frequency to check dose per monitor unit for linear accelerator photon beams
Once a month
Treatment time for 1000 cGy with Sr-90 eye applicator after 2 years
222 seconds
Daily dose delivered to the isocenter in an optimized plan
90 : 45 : 45
Density of muscle tissue
Approximately 1.03 g/cc
Accelerator component for high-power microwave energy pulses
Klystron supplies pulses to accelerate electrons
Ratio of scattered dose to effective primary dose at a point in a phantom
Tissue-maximum ratio (TMR)
Actual size of an object from radiograph measurements
10.8 cm
Relative skin dose behavior for a given energy photon beam
Increases with increasing field size
Orthogonal angles for radiographs
0 and 180 degrees
Use of tissue-maximum ratio (TMR) for megavoltage beams
Depth of maximum dose shifts as energy increases
Classification of indirectly ionizing radiation
Alpha particles
LD 50/60 definition in hematopoietic syndrome context
Allogenic marrow transplant can be life-saving for exposures 3 times the LD 50/60
Rationale for hyperfractionated radiation therapy
Normal late responding tissue divide faster, therefore recover faster
Quality factor (QF) for high-energy X rays compared to gamma rays
, 1.000
Total dose at a depth of 1.2 cm for a 4 MV linear accelerator treatment
64.7 Gy
Corrected reading per monitor unit for a secondary dosimeter
0.997
Shoulder on survival curve
Indicates reduced efficiency of cell killing at low doses
Total body irradiation
Most important dose-limiting tissue is the lung
Linear attenuation coefficient
0.51 cm-1 for a 6 MV beam
Morbidity in lung cancer treatment
Includes pericarditis
Inadvertent 18 MV treatment
Delivers 225 cGy to 5 cm depth
Total CNS technique
Requires non-divergent beam junctions
Mechanical isocenter location
Determined by rotating the gantry around a pointer
Waveguide component
Directs electron beam to the output window
Off-axis ratio
Represents the dose ratio at off-axis point to central axis at the same depth
Density of fat
Approximately 0.95 g/cc
Activity of Cesium-137 source
After 6.5 years, will be 21.5 mCi
Stochastic effect of radiation
Example is decreased sperm count
Enface electron beam dose
Increased due to an increase in the electron fluence
Ionization chamber readings
Monitor unit setting is 217 MU for 6 cm x 10 cm cut-out
Secular equilibrium
Occurs when parent and daughter isotopes have a constant ratio of activity
Inhomogeneity corrections in treatment plans
TPS converts CT numbers to Hounsfield units
Avoiding cord overdose
Achieved by angling lateral fields off the cord
Annual equivalent dose limit for hands
According to NCRP guidelines #116, is 50 mSv (5.0 rem)
Photoelectric interactions
Entire energy of incident photon is absorbed by resulting electron
Film badges in personnel monitoring
Contain filters to reduce dose from low-energy radiations
Prognostic factor in breast cancer
Density of healthy lung tissue
Approximately 1.00 g/cc
Accelerator component for electron injection
Electron gun injects electrons into the linear accelerator
Time post-fertilization for severe birth defects
13 - 24 weeks
Decay constant for a 60-day half-life source
0.662
Function of a maze in a treatment room
Minimize radiation levels at the door
Anatomic location of seminal vesicles
Inferior to the prostate, angled posteriorly near the rectum
Missed treatment days due to LINAC malfunction
May be compensated by adding fractions with weekend treatment if possible
Lowest dose delivery to femoral heads in 4-field box technique
100 source-to-axis distance (SAD), equal target dose to all fields
Frequency to check dose per monitor unit for linear accelerator photon beams
Once a month
Treatment time for 1000 cGy with Sr-90 eye applicator after 2 years
222 seconds
Daily dose delivered to the isocenter in an optimized plan
90 : 45 : 45
Density of muscle tissue
Approximately 1.03 g/cc
Accelerator component for high-power microwave energy pulses
Klystron supplies pulses to accelerate electrons
Ratio of scattered dose to effective primary dose at a point in a phantom
Tissue-maximum ratio (TMR)
Actual size of an object from radiograph measurements
10.8 cm
Relative skin dose behavior for a given energy photon beam
Increases with increasing field size
Orthogonal angles for radiographs
0 and 180 degrees
Use of tissue-maximum ratio (TMR) for megavoltage beams
Depth of maximum dose shifts as energy increases
Classification of indirectly ionizing radiation
Alpha particles
LD 50/60 definition in hematopoietic syndrome context
Allogenic marrow transplant can be life-saving for exposures 3 times the LD 50/60
Rationale for hyperfractionated radiation therapy
Normal late responding tissue divide faster, therefore recover faster
Quality factor (QF) for high-energy X rays compared to gamma rays
, 1.000
Total dose at a depth of 1.2 cm for a 4 MV linear accelerator treatment
64.7 Gy
Corrected reading per monitor unit for a secondary dosimeter
0.997
Shoulder on survival curve
Indicates reduced efficiency of cell killing at low doses
Total body irradiation
Most important dose-limiting tissue is the lung
Linear attenuation coefficient
0.51 cm-1 for a 6 MV beam
Morbidity in lung cancer treatment
Includes pericarditis
Inadvertent 18 MV treatment
Delivers 225 cGy to 5 cm depth
Total CNS technique
Requires non-divergent beam junctions
Mechanical isocenter location
Determined by rotating the gantry around a pointer
Waveguide component
Directs electron beam to the output window
Off-axis ratio
Represents the dose ratio at off-axis point to central axis at the same depth
Density of fat
Approximately 0.95 g/cc
Activity of Cesium-137 source
After 6.5 years, will be 21.5 mCi
Stochastic effect of radiation
Example is decreased sperm count
Enface electron beam dose
Increased due to an increase in the electron fluence
Ionization chamber readings
Monitor unit setting is 217 MU for 6 cm x 10 cm cut-out
Secular equilibrium
Occurs when parent and daughter isotopes have a constant ratio of activity
Inhomogeneity corrections in treatment plans
TPS converts CT numbers to Hounsfield units
Avoiding cord overdose
Achieved by angling lateral fields off the cord
Annual equivalent dose limit for hands
According to NCRP guidelines #116, is 50 mSv (5.0 rem)
Photoelectric interactions
Entire energy of incident photon is absorbed by resulting electron
Film badges in personnel monitoring
Contain filters to reduce dose from low-energy radiations
Prognostic factor in breast cancer
