MDCB test questions with verified answers
A dose of 30 Gy in 10 fractions to a depth of 7 cm from a 6 MV single
posterior field using an isocentric technique at 100 cm source-to-axis
distance (SAD). The patient was incorrectly treated five times at 100 cm
source-to-surface distance (SSD). The approximate dose at 7 cm after
five fractions is: Ans✓✓✓ 13.1 Gy.
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: Ans✓✓✓
daily.
According to the NCRP guidelines #116, the annual equivalent dose
limit for the hands of an occupational worker in 1 year is: Ans✓✓✓ 500
mSv (50.0 rem).
An averaged ionization chamber reading for a 10 cm x 10 cm electron
applicator is 98.5 and an averaged ionization chamber reading for an
electron cut-out in a 6 cm x 10 cm applicator is 92.4. What is the
monitor unit setting if 200 cGy is prescribed to 90% and the 6 cm x 10
cm cut-out is utilized? (The output factor for 10 cm x 10 cm is 1
cGy/MU.) Ans✓✓✓ 237 MU
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: Ans✓✓✓ 9.8 cm.
, 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? Ans✓✓✓ 95 : 47 :
47
An unsealed chamber used as a secondary dosimeter gives a reading of
101.0 for a 100 monitor unit exposure at a field size of 10 cm2. If the
ambient temperature is 25 degrees C and the atmospheric pressure is
770 mm Hg, the corrected reading per monitor unit is: Ans✓✓✓ 1.007
Based on clinical experience with total body irradiation (TBI) before
bone marrow transplantation and hemibody irradiation, the most
important dose-limiting tissue is the: Ans✓✓✓ lung.
Electron arc therapy is most useful for treating tumors of the Ans✓✓✓
chest wall.
Electron beam output factors are corrected for by using which of the
following? Ans✓✓✓ virtual source distance
Film badges used for personnel monitoring contain filters that are used
to: Ans✓✓✓ provide information concerning beam quality.
A dose of 30 Gy in 10 fractions to a depth of 7 cm from a 6 MV single
posterior field using an isocentric technique at 100 cm source-to-axis
distance (SAD). The patient was incorrectly treated five times at 100 cm
source-to-surface distance (SSD). The approximate dose at 7 cm after
five fractions is: Ans✓✓✓ 13.1 Gy.
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: Ans✓✓✓
daily.
According to the NCRP guidelines #116, the annual equivalent dose
limit for the hands of an occupational worker in 1 year is: Ans✓✓✓ 500
mSv (50.0 rem).
An averaged ionization chamber reading for a 10 cm x 10 cm electron
applicator is 98.5 and an averaged ionization chamber reading for an
electron cut-out in a 6 cm x 10 cm applicator is 92.4. What is the
monitor unit setting if 200 cGy is prescribed to 90% and the 6 cm x 10
cm cut-out is utilized? (The output factor for 10 cm x 10 cm is 1
cGy/MU.) Ans✓✓✓ 237 MU
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: Ans✓✓✓ 9.8 cm.
, 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? Ans✓✓✓ 95 : 47 :
47
An unsealed chamber used as a secondary dosimeter gives a reading of
101.0 for a 100 monitor unit exposure at a field size of 10 cm2. If the
ambient temperature is 25 degrees C and the atmospheric pressure is
770 mm Hg, the corrected reading per monitor unit is: Ans✓✓✓ 1.007
Based on clinical experience with total body irradiation (TBI) before
bone marrow transplantation and hemibody irradiation, the most
important dose-limiting tissue is the: Ans✓✓✓ lung.
Electron arc therapy is most useful for treating tumors of the Ans✓✓✓
chest wall.
Electron beam output factors are corrected for by using which of the
following? Ans✓✓✓ virtual source distance
Film badges used for personnel monitoring contain filters that are used
to: Ans✓✓✓ provide information concerning beam quality.
