Unit IV: Dosimetry questions with verified answers
Ans✓✓✓ A Gross tumor volume
B Treated volume
C Irradiated volume
D Clinical target volume
E Planning target volume
_______ corrections account for the dose effects produced by the
presence of materials of density different than water or unit density:
Ans✓✓✓ heterogeneity
(5)ratio of absorbed dose at a given depth in a phantom to the
absorbed dose at the same point in free space Ans✓✓✓ TAR
`The proper sequence in which an electron travels through the
treatment head of a linear accelerator when treating with an electron
beam is:
1. Ion chamber
2. Scattering foil
3. Secondary collimator Ans✓✓✓ 2, 1, 3
1 Gy is equal to: Ans✓✓✓ 1 J/kg
,172 MU are required to deliver 150cGy. 200 MU were accidentally
given. How many cGy did the patient receive? Ans✓✓✓ 174
200kv
10 MV
1.25MV (Co-60)
24 MV
6 MV
18 MV
4 MV Ans✓✓✓ 0
2.5
0.5
4.0
1.5
3.5
1.0
4.5 cm Ans✓✓✓ 5.4 cm
A ___ is the use of independent variable secondary collimator jaws
moving during treatment. Ans✓✓✓ dynamic wedge
,A 4MV linear accelerator is used at 100cm SSD. The location of
maximum dose is found at a depth of: Ans✓✓✓ 1.0cm
A 6MV linear accelerator is used at 100cm SSD. The location of
maximum dose is found at a depth of: Ans✓✓✓ 1.5cm
A bulge on the lateral region of the isodose curve at depth is most often
associated with: Ans✓✓✓ low energy photon beams
A course of radiation therapy which is intended to relieve the suffering
of an individual with no intent to cure is called a: Ans✓✓✓ palliative
therapy
A craniospinal patient is being treated on the 6MV machine with 100cm
SAD using the following field sizes. The patient separation is 16cm and
the field is being treated midplane.
Rt. Lat Brain: x1= 11.0cm and x2 = 11.0cm; y1= 0.cm and y2= 17.0cm.
Ans✓✓✓ no collimation needed
A dose of 200 cGy is to be delivered to the 95% isodose curve using a 9
MeV electron beam and 10 x 10 cm cone. The election insert treatment
field size is 6 x 7 cm and the SSD is 100 cm. The dose rate is 0.780
cGy/MU for the electron insert. Calculate the MU required. Ans✓✓✓
270
, 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✓✓✓ 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✓✓✓
10.5cm
A lesion is treated using a 100 degree arc and the midpoint of the
tumor volume is 8.0 cm below skin surface. The isocenter should be
placed at least __________ below the skin surface: Ans✓✓✓ 11 cm
A megavoltage beam is defined as x-ray or electron source that has an
energy above Ans✓✓✓ 10^6 eV
A patient has to be treated at 110cm SSD in order to obtain the field
size. The doserate at the standard distance of 100cm for the same field
size is 1.043cGy/mu. What is the doserate at 110cm? Ans✓✓✓
0.862cGy/mu
Ans✓✓✓ A Gross tumor volume
B Treated volume
C Irradiated volume
D Clinical target volume
E Planning target volume
_______ corrections account for the dose effects produced by the
presence of materials of density different than water or unit density:
Ans✓✓✓ heterogeneity
(5)ratio of absorbed dose at a given depth in a phantom to the
absorbed dose at the same point in free space Ans✓✓✓ TAR
`The proper sequence in which an electron travels through the
treatment head of a linear accelerator when treating with an electron
beam is:
1. Ion chamber
2. Scattering foil
3. Secondary collimator Ans✓✓✓ 2, 1, 3
1 Gy is equal to: Ans✓✓✓ 1 J/kg
,172 MU are required to deliver 150cGy. 200 MU were accidentally
given. How many cGy did the patient receive? Ans✓✓✓ 174
200kv
10 MV
1.25MV (Co-60)
24 MV
6 MV
18 MV
4 MV Ans✓✓✓ 0
2.5
0.5
4.0
1.5
3.5
1.0
4.5 cm Ans✓✓✓ 5.4 cm
A ___ is the use of independent variable secondary collimator jaws
moving during treatment. Ans✓✓✓ dynamic wedge
,A 4MV linear accelerator is used at 100cm SSD. The location of
maximum dose is found at a depth of: Ans✓✓✓ 1.0cm
A 6MV linear accelerator is used at 100cm SSD. The location of
maximum dose is found at a depth of: Ans✓✓✓ 1.5cm
A bulge on the lateral region of the isodose curve at depth is most often
associated with: Ans✓✓✓ low energy photon beams
A course of radiation therapy which is intended to relieve the suffering
of an individual with no intent to cure is called a: Ans✓✓✓ palliative
therapy
A craniospinal patient is being treated on the 6MV machine with 100cm
SAD using the following field sizes. The patient separation is 16cm and
the field is being treated midplane.
Rt. Lat Brain: x1= 11.0cm and x2 = 11.0cm; y1= 0.cm and y2= 17.0cm.
Ans✓✓✓ no collimation needed
A dose of 200 cGy is to be delivered to the 95% isodose curve using a 9
MeV electron beam and 10 x 10 cm cone. The election insert treatment
field size is 6 x 7 cm and the SSD is 100 cm. The dose rate is 0.780
cGy/MU for the electron insert. Calculate the MU required. Ans✓✓✓
270
, 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✓✓✓ 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✓✓✓
10.5cm
A lesion is treated using a 100 degree arc and the midpoint of the
tumor volume is 8.0 cm below skin surface. The isocenter should be
placed at least __________ below the skin surface: Ans✓✓✓ 11 cm
A megavoltage beam is defined as x-ray or electron source that has an
energy above Ans✓✓✓ 10^6 eV
A patient has to be treated at 110cm SSD in order to obtain the field
size. The doserate at the standard distance of 100cm for the same field
size is 1.043cGy/mu. What is the doserate at 110cm? Ans✓✓✓
0.862cGy/mu
