Advanced Physics for Brachytherapy 2018

TLD: absorbed dose energy dependence

• TLD dose changes more than water at Q<

) ( Q TLDDQwD

) (

QQ rel f =

)0 , (

Q TLD DQwD

) 0(

)0(

) ( Q w

(





)

TLD en

, ( Q Q rel f

)0 =



7.0

Q w

(





)

)0(

TLD en

for LDR sources relative to Co-60.

This is only an approximation.

MC is used to account for: • photon spectra @ each point in Q, Q 0 • TLD attenuation, • v. averaging • cavity corrections, … etc. See: Rodriguez and Rogers, Med. Phys. 41(11) p. 114301 (2014) for an excellent review…!

Figure from: Rogers & Cygler (Eds), Clinical dosimetry measurements in radiotherapy (2009 AAPM Summer School), Monograph No. 34, Medical Physics Publishing 2011