Dosimetry Unit 1 Exam questions with verified
answers
175 cGy have been prescribed to a midplane depth using a single
posterior field. the field size is 22 cm x 29 cm and the custom blocks are
being used. the output factor is 1.035, TMR is 0.953, and the
transmission factor for the block is 0.976. if the patients seperation is
32 cm, calculate the monitor units needed per field Ans✓✓✓ 181.78
MU
a patient is being treated AP/PA to a total dose of 4500 cGy. if the fields
are weighted 2:1.5, what is the total dose contribution from the
anterior field? Ans✓✓✓ 2571.4 cGy
a patient is being treated with craniospinal axis radiation therapy. if the
cranial field has a total length of 24 cm and is treated at 100 SSD and
the spinal field is 16 cm in length and is also to be treated at 100 SSD
calculate the skin gap if the fields are to converge at a depth of 8 cm
Ans✓✓✓ 1.6 cm
a patient is to be treated on a 100 cm SAD linear accelerator. if the
patients thickness measures 29 cm anterior to posterior and the
anterior SSD reads 89 cm, what does the PA SSD read? Ans✓✓✓ 82 cm
a patient is treated at 100 cm SAD with a 6 MV beam. the patient is
treated with an anterior field and right and left lateral fields. a 45
degree wedge is used with each lateral field. the anterior field is set to
, 91 cm SSD. each lateral field is set to 89 cm SSD. the anterior field
collimator setting is 20 x 20 cm. the MLC is used to create an 11 x 11
EFS. the collimator setting for the lateral fields is 7 x 13 cm. the MLC
used to create a 5 x 5 EFS. the prescription calls for 195 cGy to be
delivered at 65 cGy per field daily. calculate the MU setting Ans✓✓✓ i
got this wrong (#29)
a patient is treated at 100 cm SAD with a single 6 MV beam. the
treatment SSD is 93 cm. the collimator setting is 19 x 19 cm, and the
field is blocked to a 14 x 14 EFS. a 5 mm slotted tray is used to support
the block. the prescription calls for 180 cGy to be delivered daily.
calculate the MU setting with use of TAR Ans✓✓✓ 193.5 MU
a patient is treated on the 6 MV linear accelerator at 100 cm SAD. the
treatment SSD is 87 cm. the collimator setting is 17 x 17 cm. no beam
shaping is used for this treatment. the prescription states that a dose of
7000 cGy is to be delivered to a depth of 9 cm in 30 fractions through a
single field. calculate the MU setting with use of TMR Ans✓✓✓ 264.97
MU
a patient is treated on the 6 MV linear accelerator at 100 cm SSD. the
collimator setting is 13 x 13 cm. the MLC reduces the treated area to 9 x
9 EFS. the prescription states that a dose of 6500 cGy is to be
delievedred to a depth of 14 cm in 25 fractions using an AP/PA
treatment field arrangement. the patients central axis seperation is 28
cm. the spinal cord lies 5 cm beneath the posterior skin surface.
calculate the total dmax and cord dose Ans✓✓✓ idk dmax, cord is 79.3
answers
175 cGy have been prescribed to a midplane depth using a single
posterior field. the field size is 22 cm x 29 cm and the custom blocks are
being used. the output factor is 1.035, TMR is 0.953, and the
transmission factor for the block is 0.976. if the patients seperation is
32 cm, calculate the monitor units needed per field Ans✓✓✓ 181.78
MU
a patient is being treated AP/PA to a total dose of 4500 cGy. if the fields
are weighted 2:1.5, what is the total dose contribution from the
anterior field? Ans✓✓✓ 2571.4 cGy
a patient is being treated with craniospinal axis radiation therapy. if the
cranial field has a total length of 24 cm and is treated at 100 SSD and
the spinal field is 16 cm in length and is also to be treated at 100 SSD
calculate the skin gap if the fields are to converge at a depth of 8 cm
Ans✓✓✓ 1.6 cm
a patient is to be treated on a 100 cm SAD linear accelerator. if the
patients thickness measures 29 cm anterior to posterior and the
anterior SSD reads 89 cm, what does the PA SSD read? Ans✓✓✓ 82 cm
a patient is treated at 100 cm SAD with a 6 MV beam. the patient is
treated with an anterior field and right and left lateral fields. a 45
degree wedge is used with each lateral field. the anterior field is set to
, 91 cm SSD. each lateral field is set to 89 cm SSD. the anterior field
collimator setting is 20 x 20 cm. the MLC is used to create an 11 x 11
EFS. the collimator setting for the lateral fields is 7 x 13 cm. the MLC
used to create a 5 x 5 EFS. the prescription calls for 195 cGy to be
delivered at 65 cGy per field daily. calculate the MU setting Ans✓✓✓ i
got this wrong (#29)
a patient is treated at 100 cm SAD with a single 6 MV beam. the
treatment SSD is 93 cm. the collimator setting is 19 x 19 cm, and the
field is blocked to a 14 x 14 EFS. a 5 mm slotted tray is used to support
the block. the prescription calls for 180 cGy to be delivered daily.
calculate the MU setting with use of TAR Ans✓✓✓ 193.5 MU
a patient is treated on the 6 MV linear accelerator at 100 cm SAD. the
treatment SSD is 87 cm. the collimator setting is 17 x 17 cm. no beam
shaping is used for this treatment. the prescription states that a dose of
7000 cGy is to be delivered to a depth of 9 cm in 30 fractions through a
single field. calculate the MU setting with use of TMR Ans✓✓✓ 264.97
MU
a patient is treated on the 6 MV linear accelerator at 100 cm SSD. the
collimator setting is 13 x 13 cm. the MLC reduces the treated area to 9 x
9 EFS. the prescription states that a dose of 6500 cGy is to be
delievedred to a depth of 14 cm in 25 fractions using an AP/PA
treatment field arrangement. the patients central axis seperation is 28
cm. the spinal cord lies 5 cm beneath the posterior skin surface.
calculate the total dmax and cord dose Ans✓✓✓ idk dmax, cord is 79.3
