MDCB Exam Study Guide Questions with
Correct Answers
(T/F) In SAD techniques, the beams are weighted at dmax point. - Correct Answer False
(T/F) In SAD techniques, the beams are weighted at target center. - Correct Answer False
(T/F) Isodose or PDD data can be used directly for a patient, without any modification. - Correct
Answer False
(T/F) TAR concept is usually not used with accelerator photon beams because the dose in free air is
not well defined due to conceptual difficulties - Correct Answer True
(T/F) TAR can be measured directly or derived from the PDD data. - Correct Answer True
(T/F) In general TAR increases with increase in depth. - Correct Answer False
(T/F) At orthovoltage beam quality's (>about 0.5 mm Cu HVL) BSF increases with an increase in
energy. - Correct Answer False
(T/F) TAR decreases with increase in field size. - Correct Answer False
(T/F) Exit dose calculated using the standard PDD tables would give the correct exit dose. - Correct
Answer False
(T/F) The off axis ratio is the dose at any point in a plane perpendicular to the central axis to that of
the dose on the central axis in that plane. - Correct Answer True
(T/F) At a phantom depth of 10 cm, on the central axis, scatter contribution to the dose is more for
an accelerator photon beam compared to a Co60‐b eam. - Correct Answer False
(T/F) At any depth, the scatter contribution to total dose decreases with increase in incident photon
energy - Correct Answer True
,(T/F) Cross‐beam profile can give information regarding field size, physical penumbra, beam flatness,
and symmetry. - Correct Answer True
(T/F) A wedge in motion is known as a dynamic wedge. - Correct Answer False
(T/F) The energy fluence of the photons falls according to the inverse square law of distance with the
source position as the origin. - Correct Answer True
(T/F) Photon beams have a finite range in a patient. - Correct Answer False
(T/F) In the AAPM TG‐51 protocol, the electron beam quality is specified by E0 , the mean energy of
the electrons incident on the patient. - Correct Answer False
(T/F) The field size dependence of the PDD of an accelerator photon beam is very much influence d
by the electron contamination of the beam - Correct Answer True
(T/F) Scatter generally decreases PDD. - Correct Answer False
(T/F) Half blocked tangential breast treatments can be easily accomplished with independent jaw
movements. - Correct Answer True
(T/F) One of the advantages of a dynamic wedge over a physical wedge for treatment is that there is
no change in beam quality across the field size. - Correct Answer True
(T/F) The tail of the electron beam depth dose distribution is due to some long ‐range electrons in
the beam. - Correct Answer False
(T/F) Electron beams have a finite range in medium. - Correct Answer True
(T/F) Low‐energy electrons are more easily scattered compared to high‐energy electrons. - Correct
Answer True
The beam output (cGy/min) measured in air for a Co ‐60 unit increases with field size mainly due to:
collimator scatter
,room scatter
couch backscatter
chamber wall scatter - Correct Answer collimator scatter
Disadvantages of using a physical wedge include:
hardening of the beam, which also depends on wedge thickness
difficulty in positioning the wedge reproducibly in the beam path
attenuation of the beam and an increase in treatment time
inconvenience in handling heavy wedges - Correct Answer hardening of the beam, which also
depends on wedge thickness
attenuation of the beam and an increase in treatment time
inconvenience in handling heavy wedges
In case of isocentric treatment, compared to constant SSD method:
setup
‐ti me decreases
setup
‐e orre r dc r eases
treatment accuracy increases
overall time to treat a patient increases - Correct Answer set‐up time decreases
setup
‐e orre r dc r eases
treatment accuracy increases
The TAR:
, concept is usually not preferred with accelerator photon beams because the dose in free air is not
well defined for these beams
can be derived from PDD data
at dmax and PSF are practically the same quantity
always increases with depth - Correct Answer concept is usually not preferred with accelerator
photon beams because the dose in free air is not well defined for these beams
can be derived from PDD data
at dmax and PSF are practically the same quantity
The side of an equivalent square of a rectangular field (a cm x b cm) is approximately:
2ab/a+b
sqrt(ab)
(a+b)/2
none of the above - Correct Answer 2ab/a+b
TMR depends on:
depth
field size
beam quality
SSD - Correct Answer depth
field size
beam quality
Collimator scatter Sc( r ), provides the:
output factor in air
influence of head scatter on beam output, with increasing collimator field size
Correct Answers
(T/F) In SAD techniques, the beams are weighted at dmax point. - Correct Answer False
(T/F) In SAD techniques, the beams are weighted at target center. - Correct Answer False
(T/F) Isodose or PDD data can be used directly for a patient, without any modification. - Correct
Answer False
(T/F) TAR concept is usually not used with accelerator photon beams because the dose in free air is
not well defined due to conceptual difficulties - Correct Answer True
(T/F) TAR can be measured directly or derived from the PDD data. - Correct Answer True
(T/F) In general TAR increases with increase in depth. - Correct Answer False
(T/F) At orthovoltage beam quality's (>about 0.5 mm Cu HVL) BSF increases with an increase in
energy. - Correct Answer False
(T/F) TAR decreases with increase in field size. - Correct Answer False
(T/F) Exit dose calculated using the standard PDD tables would give the correct exit dose. - Correct
Answer False
(T/F) The off axis ratio is the dose at any point in a plane perpendicular to the central axis to that of
the dose on the central axis in that plane. - Correct Answer True
(T/F) At a phantom depth of 10 cm, on the central axis, scatter contribution to the dose is more for
an accelerator photon beam compared to a Co60‐b eam. - Correct Answer False
(T/F) At any depth, the scatter contribution to total dose decreases with increase in incident photon
energy - Correct Answer True
,(T/F) Cross‐beam profile can give information regarding field size, physical penumbra, beam flatness,
and symmetry. - Correct Answer True
(T/F) A wedge in motion is known as a dynamic wedge. - Correct Answer False
(T/F) The energy fluence of the photons falls according to the inverse square law of distance with the
source position as the origin. - Correct Answer True
(T/F) Photon beams have a finite range in a patient. - Correct Answer False
(T/F) In the AAPM TG‐51 protocol, the electron beam quality is specified by E0 , the mean energy of
the electrons incident on the patient. - Correct Answer False
(T/F) The field size dependence of the PDD of an accelerator photon beam is very much influence d
by the electron contamination of the beam - Correct Answer True
(T/F) Scatter generally decreases PDD. - Correct Answer False
(T/F) Half blocked tangential breast treatments can be easily accomplished with independent jaw
movements. - Correct Answer True
(T/F) One of the advantages of a dynamic wedge over a physical wedge for treatment is that there is
no change in beam quality across the field size. - Correct Answer True
(T/F) The tail of the electron beam depth dose distribution is due to some long ‐range electrons in
the beam. - Correct Answer False
(T/F) Electron beams have a finite range in medium. - Correct Answer True
(T/F) Low‐energy electrons are more easily scattered compared to high‐energy electrons. - Correct
Answer True
The beam output (cGy/min) measured in air for a Co ‐60 unit increases with field size mainly due to:
collimator scatter
,room scatter
couch backscatter
chamber wall scatter - Correct Answer collimator scatter
Disadvantages of using a physical wedge include:
hardening of the beam, which also depends on wedge thickness
difficulty in positioning the wedge reproducibly in the beam path
attenuation of the beam and an increase in treatment time
inconvenience in handling heavy wedges - Correct Answer hardening of the beam, which also
depends on wedge thickness
attenuation of the beam and an increase in treatment time
inconvenience in handling heavy wedges
In case of isocentric treatment, compared to constant SSD method:
setup
‐ti me decreases
setup
‐e orre r dc r eases
treatment accuracy increases
overall time to treat a patient increases - Correct Answer set‐up time decreases
setup
‐e orre r dc r eases
treatment accuracy increases
The TAR:
, concept is usually not preferred with accelerator photon beams because the dose in free air is not
well defined for these beams
can be derived from PDD data
at dmax and PSF are practically the same quantity
always increases with depth - Correct Answer concept is usually not preferred with accelerator
photon beams because the dose in free air is not well defined for these beams
can be derived from PDD data
at dmax and PSF are practically the same quantity
The side of an equivalent square of a rectangular field (a cm x b cm) is approximately:
2ab/a+b
sqrt(ab)
(a+b)/2
none of the above - Correct Answer 2ab/a+b
TMR depends on:
depth
field size
beam quality
SSD - Correct Answer depth
field size
beam quality
Collimator scatter Sc( r ), provides the:
output factor in air
influence of head scatter on beam output, with increasing collimator field size
