MDCB EXAM QUESTIONS WITH CORRECT
ANSWERS
50 QUESTIONS AND ANSWERS
What is the approximate density of healthy lung tissue? - ANSWER 0.30 g/cc
The accelerator component that injects electrons into the linear accelerator is: -
ANSWER an electron gun
Radiation damage to the fetus resulting in severe birth defects would most often
occur when radiation was delivered at which time post-fertilization? -
ANSWER 3 - 12 weeks
The decay constant for a radioactive source that has a half-life of 60 days is: -
ANSWER 0.012.
The function of a maze to a megavoltage treatment room is to: - ANSWER
minimize radiation levels at the door.
The anatomic location of the seminal vesicles is: - ANSWER superior to the
prostate and angled posteriorly near the rectum.
Two missed treatment days due to LINAC malfunction: - ANSWER may be
compensated by adding the same or even more fractions to the treatment course
with weekend treatment if possible.
For a 4-field box technique, which of the following will deliver the lowest dose
to the femoral heads? - ANSWER 100 source-to-surface distance (SSD), equal
dmax dose to all fields
According to the American Association of Physicists in Medicine (AAPM)
Task Group Report #142, the constancy of dose per monitor unit for photon
beams of a linear accelerator should be checked: - ANSWER daily.
, The surface dose rate of a Strontium-90 (Sr-90) eye applicator was 4.5
cGy/second on May 15. If a patient is to be treated 2 years later on May 15,
what is the treatment time if 1000 cGy is prescribed? (The half-life of Sr-90 is
28 years.) - ANSWER 233 seconds
An optimized plan consists of three fields weighted 1.0 : 0.5 : 0.5 at the
isocenter. The plan was normalized to the isocenter and the radiation oncologist
prescribed 4500 cGy in 25 fractions to the 95% isodose line. What daily dose
will be delivered to the isocenter? - ANSWER 95 : 47 : 47
What is the approximate density of muscle? - ANSWER 1.03 g/cc
Which of the following is the accelerator component that supplies pulses of
high-power radiofrequency microwave energy to accelerate injected electrons? -
ANSWER klystron
Which of the following represents the ratio of the scattered dose at a given point
in a phantom to the effective primary dose at the same point at the reference
depth of maximum dose? - ANSWER scatter-maximum ratio (SMR)
An image on a radiograph measures 12 cm. The source-to-object distance is 90
cm and the source-to-film distance is 110 cm. The actual size of the object is: -
ANSWER 9.8 cm.
The relative skin dose for a given energy photon beam: - ANSWER increases
with increasing field size.
Radiographs taken at which of the following sets of angles would be
orthogonal? - ANSWER 85 and 355 degrees
The tissue-maximum ratio (TMR) is used in place of the tissue-air ratio (TAR)
for megavoltage beams because, as energy increases, the: - ANSWER dose in
free space becomes difficult to measure.
Which of the following can be classified as indirectly ionizing radiation? -
ANSWER photons
ANSWERS
50 QUESTIONS AND ANSWERS
What is the approximate density of healthy lung tissue? - ANSWER 0.30 g/cc
The accelerator component that injects electrons into the linear accelerator is: -
ANSWER an electron gun
Radiation damage to the fetus resulting in severe birth defects would most often
occur when radiation was delivered at which time post-fertilization? -
ANSWER 3 - 12 weeks
The decay constant for a radioactive source that has a half-life of 60 days is: -
ANSWER 0.012.
The function of a maze to a megavoltage treatment room is to: - ANSWER
minimize radiation levels at the door.
The anatomic location of the seminal vesicles is: - ANSWER superior to the
prostate and angled posteriorly near the rectum.
Two missed treatment days due to LINAC malfunction: - ANSWER may be
compensated by adding the same or even more fractions to the treatment course
with weekend treatment if possible.
For a 4-field box technique, which of the following will deliver the lowest dose
to the femoral heads? - ANSWER 100 source-to-surface distance (SSD), equal
dmax dose to all fields
According to the American Association of Physicists in Medicine (AAPM)
Task Group Report #142, the constancy of dose per monitor unit for photon
beams of a linear accelerator should be checked: - ANSWER daily.
, The surface dose rate of a Strontium-90 (Sr-90) eye applicator was 4.5
cGy/second on May 15. If a patient is to be treated 2 years later on May 15,
what is the treatment time if 1000 cGy is prescribed? (The half-life of Sr-90 is
28 years.) - ANSWER 233 seconds
An optimized plan consists of three fields weighted 1.0 : 0.5 : 0.5 at the
isocenter. The plan was normalized to the isocenter and the radiation oncologist
prescribed 4500 cGy in 25 fractions to the 95% isodose line. What daily dose
will be delivered to the isocenter? - ANSWER 95 : 47 : 47
What is the approximate density of muscle? - ANSWER 1.03 g/cc
Which of the following is the accelerator component that supplies pulses of
high-power radiofrequency microwave energy to accelerate injected electrons? -
ANSWER klystron
Which of the following represents the ratio of the scattered dose at a given point
in a phantom to the effective primary dose at the same point at the reference
depth of maximum dose? - ANSWER scatter-maximum ratio (SMR)
An image on a radiograph measures 12 cm. The source-to-object distance is 90
cm and the source-to-film distance is 110 cm. The actual size of the object is: -
ANSWER 9.8 cm.
The relative skin dose for a given energy photon beam: - ANSWER increases
with increasing field size.
Radiographs taken at which of the following sets of angles would be
orthogonal? - ANSWER 85 and 355 degrees
The tissue-maximum ratio (TMR) is used in place of the tissue-air ratio (TAR)
for megavoltage beams because, as energy increases, the: - ANSWER dose in
free space becomes difficult to measure.
Which of the following can be classified as indirectly ionizing radiation? -
ANSWER photons
