MDCB Practice Exam
What factors are instrumental in determining the dose uniformity in equally weighted
parallel opposed beams?
A. beam energy, tissue inhomogeneity and patient thickness
B. beam energy, patient thickness and tissue maximum ratio
C. beam flatness, patient thickness and collimator scatter
D. patient thickness, inhomogeneity and collimator scatter - answerA. beam energy,
tissue inhomogeneity and patient thickness
Two adjacent electron fields are to be used to treat a post-mastectomy chestwall. The
radiation oncologist has expressed concern that a cold spot at the surface be avoided.
Appropriate techniques include which of the following?
A. Match the fields at the Dmax depth of the electron fields.
B. Match the fields with a 0.5 cm overlap.
C. Move the junction several times during the treatment course.
D. Match the fields with a gap of 0.5 cm at the skin surface. - answerC. Move the
junction several times during the treatment course.
Characteristics of MLC, in current medical LINACs, include which of the following:
A. accommodates all field sizes.
B. "scalloped" isodose curves in the penumbra region.
C. ability to conform to all possible field shapes.
D. inability to verify leaf shapes. - answerB. "scalloped" isodose curves in the penumbra
region.
When treating with electrons typical X-ray contamination dose to a patient ranges from
approximately:
A. 0.1% to 0.4%
B. 0.5% to 5%
C. 6% to 9%
D. 10% to 12% - answerB. 0.5% to 5%
Rounded ends on the leaves of a multi-leaf collimator are used to:
A. enhance field shaping potential.
B. achieve a constant tissue-air ratio.
C. reduce interleaf leakage.
D. achieve a constant penumbra as field size varies. - answerD. achieve a constant
penumbra as field size varies.
The installation of any new treatment planning system requires the acceptance testing
of which of the following?
A. processing speed
,B. software
C. power consumption
D. memory capacity - answerB. software
Which of the following statements is/are TRUE concerning radiation warning signs?
A. Only the term "Danger" may be used in "Radiation Areas".
B. The terms "Caution" or "Danger" may be used in "High Radiation Areas".
C. Only the term "Danger" may be used in "Very High Radiation Areas".
D. Only the color scheme of magenta or purple on yellow is acceptable for use on
warning signs. - answerB. The terms "Caution" or "Danger" may be used in "High
Radiation Areas".
Based on NCRP recommendations, which of the following is a guideline regarding
pregnancy and radiation exposure?
A. The fetus can be considered as an occupationally exposed individual.
B. The exposure to the fetus should not exceed 50 mSv for the entire gestational period.
C. The exposure to the fetus should not exceed 5 mSv in any one month.
D. Pregnant medical radiation workers can be considered occupationally exposed
individuals. - answerD. Pregnant medical radiation workers can be considered
occupationally exposed individuals.
When an isocentric technique is used in place of an SSD technique (both beams treated
at 100SSD) to deliver the same midpoint dose to a patient with two parallel opposed
fields, the:
A. relative skin dose is decreased
B. number of monitor units for both fields is increased
C. field size at the patient's surface must be increased to treat the same volume of
tissue
D. ratio of maximum dose to midpoint dose is increased - answerD. ratio of maximum
dose to midpoint dose is increased
Computerized MU calculations for delivery of the prescribed dose to a point near a
block need special care for which of the following reasons?
A. The calculation point may be projected under the block.
B. Electron scatter from the block is not accounted by the computer.
C. The block reduces scatter in the field.
D. A steep dose gradient exists near the block. - answerD. A steep dose gradient exists
near the block.
Which of the following statements is CORRECT regarding the concept of equivalent
squares in dose calculation?
A. A rectangular field is equivalent to a square field if they have the same
Area/Perimeter ratio.
B. A rectangular photon field has the same output and percentage depth dose (PDD) as
a square field of the same area.
,C. Standard equivalent square table values for rectangular fields are applied to electron
output and percentage depth dose data.
D. The concept of equivalent squares is primarily useful in the determination of beam
flatness - answerA. A rectangular field is equivalent to a square field if they have the
same Area/Perimeter ratio.
The effective field size for a 10x10 field size, with 30% blocked is approximately how
many cm2?
A. 5.5
B. 6.5
C. 7.5
D. 8.5 - answerD. 8.5
Which of the following statements regarding geometric penumbra is TRUE?
A. Penumbra size is not dependent on the source size.
B. The penumbra decreases as block-to-skin distance increases, all other factors being
equal.
C. The penumbra increases as the distance from the source increases, all other factors
being equal.
D. In general, the penumbra will become sharper on an accelerator as the collimator
setting is increased. - answerC. The penumbra increases as the distance from the
source increases, all other factors being equal.
Which of the following is a potential late toxicity of pre-operative radiotherapy in the
treatment of rectal carcinoma?
A. small-bowel obstruction.
B. polycythemia.
C. lymphedema
D. bladder perforation. - answerA. small-bowel obstruction.
11. According to the RTOG Breast Cancer Atlas, the contour of the Breast CTV should
include the:
A. apparent glandular tissue and axillary lymph node regions.
B. apparent glandular tissue and tissue outlined by conventional anatomic markers.
C. lumpectomy GTV, including the surgical scar.
D. lumpectomy CTV + 1 cm margin. - answerB. apparent glandular tissue and tissue
outlined by conventional anatomic markers.
14. The surface dose for 6 MeV electron beam, based on a 10x10 cm2 field size, is:
A. 75%.
B. 85%
C. 90%
D. 95% - answerA. 75%.
When a missing tissue compensator is used in the treatment of the thorax, it will:
A. reduce the variation of dose within the field.
, B. reduce the treatment time.
C. produce increased phantom scatter.
D. necessitate a change in dose fractionation. - answerA. reduce the variation of dose
within the field.
When a parotid tumor with a depth of 5.0 cm is treated, the highest skin dose would be
delivered by which of the following?
A. a direct 6 MV photon beam
B. a direct 18 MeV electron beam
C. a 6 MV photon and 18 MeV electron mixed beam
D. a 10 MV proton beam - answerB. a direct 18 MeV electron beam
The surface dose for an 18 MeV electron beam, based on a 10x10 cm2 field size, is:
A. 75%.
B. 85%.
C. 95%.
D. 105%. - answerC. 95%.
What is the approximate therapeutic energy range for protons?
A. 6 - 18 MeV
B. 25 - 50 MeV
C. 50 - 100 MeV
D. 150 to 250.00 MeV - answerD. 150 to 250.00 MeV
Tungsten eye shields placed under the eyelid can be used to protect the eye up to what
electron beam energy?
A. 6 MeV
B. 9 MeV
C. 12 MeV
D. 15 MeV - answerB. 9 MeV
When comparing LET to RBE which of the following is TRUE:
A. Cell killing is linearly related to LET.
B. Cell killing is inversely related to LET.
C. Lower RBE at high LET is due to lower efficiency per unit dose.
D. Lower RBE at high LET is due to radio-resistance of the cell. - answerC. Lower RBE
at high LET is due to lower efficiency per unit dose.
When treating carcinoma of the bladder, the superior border of the radiation field is
limited to the superior aspect of S-1. This is to reduce toxicity to the:
A. pelvic crest.
B. small bowel.
C. kidney.
D. ureters. - answerB. small bowel.
What factors are instrumental in determining the dose uniformity in equally weighted
parallel opposed beams?
A. beam energy, tissue inhomogeneity and patient thickness
B. beam energy, patient thickness and tissue maximum ratio
C. beam flatness, patient thickness and collimator scatter
D. patient thickness, inhomogeneity and collimator scatter - answerA. beam energy,
tissue inhomogeneity and patient thickness
Two adjacent electron fields are to be used to treat a post-mastectomy chestwall. The
radiation oncologist has expressed concern that a cold spot at the surface be avoided.
Appropriate techniques include which of the following?
A. Match the fields at the Dmax depth of the electron fields.
B. Match the fields with a 0.5 cm overlap.
C. Move the junction several times during the treatment course.
D. Match the fields with a gap of 0.5 cm at the skin surface. - answerC. Move the
junction several times during the treatment course.
Characteristics of MLC, in current medical LINACs, include which of the following:
A. accommodates all field sizes.
B. "scalloped" isodose curves in the penumbra region.
C. ability to conform to all possible field shapes.
D. inability to verify leaf shapes. - answerB. "scalloped" isodose curves in the penumbra
region.
When treating with electrons typical X-ray contamination dose to a patient ranges from
approximately:
A. 0.1% to 0.4%
B. 0.5% to 5%
C. 6% to 9%
D. 10% to 12% - answerB. 0.5% to 5%
Rounded ends on the leaves of a multi-leaf collimator are used to:
A. enhance field shaping potential.
B. achieve a constant tissue-air ratio.
C. reduce interleaf leakage.
D. achieve a constant penumbra as field size varies. - answerD. achieve a constant
penumbra as field size varies.
The installation of any new treatment planning system requires the acceptance testing
of which of the following?
A. processing speed
,B. software
C. power consumption
D. memory capacity - answerB. software
Which of the following statements is/are TRUE concerning radiation warning signs?
A. Only the term "Danger" may be used in "Radiation Areas".
B. The terms "Caution" or "Danger" may be used in "High Radiation Areas".
C. Only the term "Danger" may be used in "Very High Radiation Areas".
D. Only the color scheme of magenta or purple on yellow is acceptable for use on
warning signs. - answerB. The terms "Caution" or "Danger" may be used in "High
Radiation Areas".
Based on NCRP recommendations, which of the following is a guideline regarding
pregnancy and radiation exposure?
A. The fetus can be considered as an occupationally exposed individual.
B. The exposure to the fetus should not exceed 50 mSv for the entire gestational period.
C. The exposure to the fetus should not exceed 5 mSv in any one month.
D. Pregnant medical radiation workers can be considered occupationally exposed
individuals. - answerD. Pregnant medical radiation workers can be considered
occupationally exposed individuals.
When an isocentric technique is used in place of an SSD technique (both beams treated
at 100SSD) to deliver the same midpoint dose to a patient with two parallel opposed
fields, the:
A. relative skin dose is decreased
B. number of monitor units for both fields is increased
C. field size at the patient's surface must be increased to treat the same volume of
tissue
D. ratio of maximum dose to midpoint dose is increased - answerD. ratio of maximum
dose to midpoint dose is increased
Computerized MU calculations for delivery of the prescribed dose to a point near a
block need special care for which of the following reasons?
A. The calculation point may be projected under the block.
B. Electron scatter from the block is not accounted by the computer.
C. The block reduces scatter in the field.
D. A steep dose gradient exists near the block. - answerD. A steep dose gradient exists
near the block.
Which of the following statements is CORRECT regarding the concept of equivalent
squares in dose calculation?
A. A rectangular field is equivalent to a square field if they have the same
Area/Perimeter ratio.
B. A rectangular photon field has the same output and percentage depth dose (PDD) as
a square field of the same area.
,C. Standard equivalent square table values for rectangular fields are applied to electron
output and percentage depth dose data.
D. The concept of equivalent squares is primarily useful in the determination of beam
flatness - answerA. A rectangular field is equivalent to a square field if they have the
same Area/Perimeter ratio.
The effective field size for a 10x10 field size, with 30% blocked is approximately how
many cm2?
A. 5.5
B. 6.5
C. 7.5
D. 8.5 - answerD. 8.5
Which of the following statements regarding geometric penumbra is TRUE?
A. Penumbra size is not dependent on the source size.
B. The penumbra decreases as block-to-skin distance increases, all other factors being
equal.
C. The penumbra increases as the distance from the source increases, all other factors
being equal.
D. In general, the penumbra will become sharper on an accelerator as the collimator
setting is increased. - answerC. The penumbra increases as the distance from the
source increases, all other factors being equal.
Which of the following is a potential late toxicity of pre-operative radiotherapy in the
treatment of rectal carcinoma?
A. small-bowel obstruction.
B. polycythemia.
C. lymphedema
D. bladder perforation. - answerA. small-bowel obstruction.
11. According to the RTOG Breast Cancer Atlas, the contour of the Breast CTV should
include the:
A. apparent glandular tissue and axillary lymph node regions.
B. apparent glandular tissue and tissue outlined by conventional anatomic markers.
C. lumpectomy GTV, including the surgical scar.
D. lumpectomy CTV + 1 cm margin. - answerB. apparent glandular tissue and tissue
outlined by conventional anatomic markers.
14. The surface dose for 6 MeV electron beam, based on a 10x10 cm2 field size, is:
A. 75%.
B. 85%
C. 90%
D. 95% - answerA. 75%.
When a missing tissue compensator is used in the treatment of the thorax, it will:
A. reduce the variation of dose within the field.
, B. reduce the treatment time.
C. produce increased phantom scatter.
D. necessitate a change in dose fractionation. - answerA. reduce the variation of dose
within the field.
When a parotid tumor with a depth of 5.0 cm is treated, the highest skin dose would be
delivered by which of the following?
A. a direct 6 MV photon beam
B. a direct 18 MeV electron beam
C. a 6 MV photon and 18 MeV electron mixed beam
D. a 10 MV proton beam - answerB. a direct 18 MeV electron beam
The surface dose for an 18 MeV electron beam, based on a 10x10 cm2 field size, is:
A. 75%.
B. 85%.
C. 95%.
D. 105%. - answerC. 95%.
What is the approximate therapeutic energy range for protons?
A. 6 - 18 MeV
B. 25 - 50 MeV
C. 50 - 100 MeV
D. 150 to 250.00 MeV - answerD. 150 to 250.00 MeV
Tungsten eye shields placed under the eyelid can be used to protect the eye up to what
electron beam energy?
A. 6 MeV
B. 9 MeV
C. 12 MeV
D. 15 MeV - answerB. 9 MeV
When comparing LET to RBE which of the following is TRUE:
A. Cell killing is linearly related to LET.
B. Cell killing is inversely related to LET.
C. Lower RBE at high LET is due to lower efficiency per unit dose.
D. Lower RBE at high LET is due to radio-resistance of the cell. - answerC. Lower RBE
at high LET is due to lower efficiency per unit dose.
When treating carcinoma of the bladder, the superior border of the radiation field is
limited to the superior aspect of S-1. This is to reduce toxicity to the:
A. pelvic crest.
B. small bowel.
C. kidney.
D. ureters. - answerB. small bowel.
