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TLD: absorbed dose energy dependence
)0(
)
0(
) (
) (
)0 , (
Q TLD
DQwD
Q TLDDQwD
QQ rel f
=
•
TLD dose changes more than water at Q<<Q
0
due to higher Z than water, so f
rel
<1
•
Assuming TLD is a large cavity (dimensions
large compared to max. e
-
range & small
compared to photon m.f.p.):
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…!
7.0
)0(
)
(
) (
)
(
)0
, (
=
Q w
TLD en
Q w
TLD en
Q
Q rel f
Figure from: Rogers & Cygler (Eds), Clinical dosimetry measurements in radiotherapy (2009 AAPM Summer School),
Monograph No. 34, Medical Physics Publishing 2011