ABR Quality Assurance and Quality Control

Question 1

According to AAPM TG-142, what is the daily output constancy tolerance for a linear accelerator used for non-IMRT treatments?

Accepted Answer

±2%

Answer

TG-142 specifies a ±2% daily output constancy tolerance for conventional (non-IMRT) linac treatments.

Question 2

Which AAPM task group report provides the primary framework for absolute dose calibration of high-energy photon and electron beams in the United States?

Accepted Answer

TG-51

Answer

AAPM TG-51 is the standard protocol for absorbed-dose calibration of photon and electron beams using ionization chambers in a water phantom.

Question 3

The Winston-Lutz test is primarily used to verify which parameter of a linear accelerator?

Accepted Answer

Isocenter coincidence of radiation and mechanical axes

Answer

The Winston-Lutz test verifies that the radiation isocenter coincides with the mechanical isocenter by imaging a small ball bearing at multiple gantry, collimator, and couch angles.

Question 4

According to TG-142, what is the recommended tolerance for gantry angle accuracy on a linac?

Accepted Answer

0.5°

Answer

TG-142 recommends a ±0.5° tolerance for gantry angle accuracy under monthly QA testing.

Question 5

What is the standard source-to-surface distance (SSD) reference condition used for linac output calibration per TG-51?

Accepted Answer

100 cm SSD, 10×10 cm² field, 10 cm depth

Answer

TG-51 calibration is performed at 100 cm SSD, a 10×10 cm² field size, and a reference depth of 10 cm in a water phantom.

ABR - American Board of Radiology Medical Physics Exam Practice Test

ABR - American Board of Radiology Medical Physics Exam Practice Test

ABR Quality Assurance and Quality Control