ABR ABR Radiation Dosimetry 3

Question 1

What is the output factor (Sc,p) in photon beam dosimetry a product of?

Accepted Answer

Collimator scatter factor and phantom scatter factor

Answer

PDD and TMR

Answer

Tissue-air ratio and inverse square factor

Answer

MU and dose rate

Question 2

In the TG-43 brachytherapy dosimetry formalism, what does the radial dose function g(r) describe?

Accepted Answer

Dose fall-off along the transverse axis beyond the inverse square law

Answer

Source anisotropy in polar angle

Answer

Total air kerma strength

Answer

Scatter corrections in tissue

Question 3

What quantity is used to specify the strength of a brachytherapy source in the TG-43 formalism?

Accepted Answer

Air kerma strength (SK)

Answer

Activity in mCi

Answer

Apparent activity

Answer

Exposure rate constant

Question 4

Which detector is most appropriate for measuring dose in a high dose-rate (HDR) brachytherapy treatment unit's applicator?

Accepted Answer

Well-type ionization chamber

Answer

Farmer chamber

Answer

TLD chips

Answer

Film dosimetry

Question 5

What is the clinical significance of the 'dmax' depth in a megavoltage photon beam?

Accepted Answer

It is where dose buildup ends and maximum dose occurs, used as reference for monitor unit calculations

Answer

It is where the beam enters the patient surface

Answer

It defines the 50% isodose line

Answer

It is the depth of maximum scatter

Question 6

In photon beam dosimetry, what correction factor accounts for differences between a Farmer chamber's air cavity and the reference water medium?

Accepted Answer

Perturbation correction factor (Pcav)

Answer

Polarity correction (Ppol)

Answer

Ion recombination correction (Pion)

Answer

kQ beam quality factor