ABR ABR Radiation Dosimetry

Question 1

What is the SI unit of absorbed dose used in radiation dosimetry?

Accepted Answer

Gray (Gy)

Answer

The Gray (Gy) is the SI unit of absorbed dose, defined as 1 joule of energy deposited per kilogram of tissue.

Question 2

Which type of ionization chamber is the recommended reference dosimeter for photon beam calibration per AAPM TG-51?

Accepted Answer

Farmer-type cylindrical chamber

Answer

The Farmer-type cylindrical ionization chamber is the standard reference dosimeter for photon beam calibration per the AAPM TG-51 protocol.

Question 3

In TG-51 dosimetry protocol, what reference depth is used for photon beam calibration?

Accepted Answer

10 cm

Answer

TG-51 specifies beam calibration at a reference depth of 10 cm in a water phantom for photon beams.

Question 4

What is the purpose of the kQ factor in the TG-51 calibration protocol?

Accepted Answer

Corrects for beam quality differences from the calibration standard

Answer

The kQ factor corrects the chamber's calibration coefficient from the reference 60Co beam quality to the clinical beam quality being measured.

Question 5

Which dosimetry formalism does AAPM TG-51 replace for clinical photon and electron beam calibration in the US?

Accepted Answer

TG-21

Answer

TG-51 replaced the older TG-21 protocol, transitioning from exposure-based to absorbed dose-to-water calibrations.

ABR - American Board of Radiology Medical Physics Exam Practice Test