572-573 / 2239
Phantom for plan QA: measurement vs calculation
Dose determination in phantom
Calculations of dose in phantom
Formalism to derive dose to water from from
ionisation measurements in PMMA
Chamber and medium specific perturbation factors
are for the calibration geometry and not the clinical
field
[
]
cal
scat
w
PMMA
cal
w
PMMA
en
clin
PMMA
clin
w
→
=
CF
D D
ρ
µ
cal
wall
repl
PMMA
air
air
ion
clin
PMMA
clin
PMMA
ρ
=
p p
S
N k
M D
How accurate are the HU-density conversions for plastic
phantoms?
Would it be better to create a virtual phantom with the
density of PMMA?
How does the TPSs handle materials different from water?
Does the TPS calculates dose to
PMMA in PMMA or dose
to water in PMMA?
Ma et al, PMB 48 (2003) 561-572