Dosimetric Characteristics of Clinical Photon Beams

Correction vs. Model Based Methods
Correction Based Model Based
Measured data used as basis for
Dose Computation.
Measured data used to setup
description of treatment beam.
Require measurements with buildup Require a parameter to estimate size
cap in air or in a mini-phantom. of photon source at target.
Require lots of data. Generating
functions used to reduce size of
data set for convenient clinical use
(i.e. less storage space).
Require more time for tuning of
model parameters.
p
Patient dose distribution obtained by Patient dose distribution obtained by
first computing Dose in water from
generating function, then correcting
for tissue heterogeneity, patient
contour, t and d bbeam modifiers.
difi
computing beam and beam transport
(i.e. beam interactions in treatment
head and in patient) directly.