Below are a few examples of my questions and answers for our practice problems covering TG-51 protocol and machine calibration. The correct answer is underlined and questions on which I answered wrong I include an explanation below it.
1)Ionization chambers used for machine calibration require temperature and pressure corrections to account for:
A) Variations in the mass of air in the collection volume
B) The expansion of the air at high pressure
C)The contraction of the air at high temperature
D)The contraction of the air at high temperature
E)None of the above
2)The AAPM recommends the TG-51 protocol for photon beam calibration. This protocol requires calibration to be performed in:
A)Acrylic
B)Solid water
C)Water
D)Any medium similar to muscle tissue of known composition
3)The output of a linear accelerator's photon beam is calibrated to be 1.0 cGy/MU. This calibration point is always at _____.
A)Depth dmax, 100 cm SSD, 10 x 10 cm field size
B)Depth 10 cm, 100 cm SSD, 10 x 10 cm field size
C)Depth dmax, 100 cm SAD, 10 x 10 cm field size
D) Depth 10 cm, 100 cm SAD, 10 x 10 cm field size
E) A depth, distance, and field size specified by the physicist, consistent with data used for treatment planning
-I answered wrong for this question and chose B. I was thinking about the standard approach for TG-51 protocol but TG-51 isn't specified here. Not to mention SSD or SAD setups can be used based on preference.
1)Ionization chambers used for machine calibration require temperature and pressure corrections to account for:
A) Variations in the mass of air in the collection volume
B) The expansion of the air at high pressure
C)The contraction of the air at high temperature
D)The contraction of the air at high temperature
E)None of the above
2)The AAPM recommends the TG-51 protocol for photon beam calibration. This protocol requires calibration to be performed in:
A)Acrylic
B)Solid water
C)Water
D)Any medium similar to muscle tissue of known composition
3)The output of a linear accelerator's photon beam is calibrated to be 1.0 cGy/MU. This calibration point is always at _____.
A)Depth dmax, 100 cm SSD, 10 x 10 cm field size
B)Depth 10 cm, 100 cm SSD, 10 x 10 cm field size
C)Depth dmax, 100 cm SAD, 10 x 10 cm field size
D) Depth 10 cm, 100 cm SAD, 10 x 10 cm field size
E) A depth, distance, and field size specified by the physicist, consistent with data used for treatment planning
-I answered wrong for this question and chose B. I was thinking about the standard approach for TG-51 protocol but TG-51 isn't specified here. Not to mention SSD or SAD setups can be used based on preference.