DOSIMETRY questions with verified answers
_____ is the measurement of radiation dose. Ans✓✓✓ dosimetry
1 Gy is equal to: Ans✓✓✓ 1 J/kg
A ____ isodose curve will have an hourglass shape of the highest
intensity isodose line. Ans✓✓✓ parallel opposed field
A dose of 3000 cGy is to be delivered at a depth of 8cm at a percent
depth dose of 76%. What is the dose to an organ at 14cm depth and a
percent depth dose of 58%? Ans✓✓✓ (3000/76%)=(x/58%)
2289 cGy
A dose of 5000cGy is to be delivered at a depth of 8cm where the
percent depth dose is 60.3. What is the dose to an underlying organ at
a depth of 10cm where the percent depth dose is 55.5? Ans✓✓✓ 4602
cGy
A lesion is being treated using an arc of 100º. If the midpoint of the
tumor volume is at 7cm, the isocenter should be placed at: Ans✓✓✓
10.5
A patient is being treated on the 18-MV beam to a PA spine at a depth
of 10 cm. The collimator setting is 10 × 13 with no blocks. The dose at
, depth is 300 cGy. What is the dose delivered to Dmax? Ans✓✓✓ 375
cGy
A patient is being treated on the linear accelerator using 6-MV, with
opposed lateral fields to the whole brain (midline). The collimator
setting is 14 × 18 with no blocks. The prescribed dose is 4000 cGy/20
fractions. The separation is 22 cm. What is the daily dose to Dmax?
Ans✓✓✓ 212 cGy
A patient is treated in SAD setup with equally weighted AP and PA fields
giving the same dose at midplane, . The patient separation is 20cm.
Which expression gives the correct dose to the patient's spinal cord,
located 4cm from the patient's posterior skin surface? Ans✓✓✓
A patient is treated midplane using AP:PA fields. The IFD is 22.0. The
field size at isocenter is 13.5 cm x 13.5 cm, what is the field size on the
patient's skin? Ans✓✓✓ 12 x 12
A patient is treated using two superiorly/inferiorly adjacent fields. The
collimator setting for the superior field is 10 cm wide by 13 cm long.
The collimator setting for the inferior field is 20 cm wide by 35 cm long.
Both fields are treated at 100 cm SSD. Calculate the gap at the skin
surface if the fields abut at a depth of 5 cm. Ans✓✓✓ 1.2
_____ is the measurement of radiation dose. Ans✓✓✓ dosimetry
1 Gy is equal to: Ans✓✓✓ 1 J/kg
A ____ isodose curve will have an hourglass shape of the highest
intensity isodose line. Ans✓✓✓ parallel opposed field
A dose of 3000 cGy is to be delivered at a depth of 8cm at a percent
depth dose of 76%. What is the dose to an organ at 14cm depth and a
percent depth dose of 58%? Ans✓✓✓ (3000/76%)=(x/58%)
2289 cGy
A dose of 5000cGy is to be delivered at a depth of 8cm where the
percent depth dose is 60.3. What is the dose to an underlying organ at
a depth of 10cm where the percent depth dose is 55.5? Ans✓✓✓ 4602
cGy
A lesion is being treated using an arc of 100º. If the midpoint of the
tumor volume is at 7cm, the isocenter should be placed at: Ans✓✓✓
10.5
A patient is being treated on the 18-MV beam to a PA spine at a depth
of 10 cm. The collimator setting is 10 × 13 with no blocks. The dose at
, depth is 300 cGy. What is the dose delivered to Dmax? Ans✓✓✓ 375
cGy
A patient is being treated on the linear accelerator using 6-MV, with
opposed lateral fields to the whole brain (midline). The collimator
setting is 14 × 18 with no blocks. The prescribed dose is 4000 cGy/20
fractions. The separation is 22 cm. What is the daily dose to Dmax?
Ans✓✓✓ 212 cGy
A patient is treated in SAD setup with equally weighted AP and PA fields
giving the same dose at midplane, . The patient separation is 20cm.
Which expression gives the correct dose to the patient's spinal cord,
located 4cm from the patient's posterior skin surface? Ans✓✓✓
A patient is treated midplane using AP:PA fields. The IFD is 22.0. The
field size at isocenter is 13.5 cm x 13.5 cm, what is the field size on the
patient's skin? Ans✓✓✓ 12 x 12
A patient is treated using two superiorly/inferiorly adjacent fields. The
collimator setting for the superior field is 10 cm wide by 13 cm long.
The collimator setting for the inferior field is 20 cm wide by 35 cm long.
Both fields are treated at 100 cm SSD. Calculate the gap at the skin
surface if the fields abut at a depth of 5 cm. Ans✓✓✓ 1.2
