Dosimetric features of linac head and phantom scattered radiation outside the clinical photon beam: experimental measurements and comparison with treatment planning system calculations
L. Cozzi et al., Dosimetric features of linac head and phantom scattered radiation outside the clinical photon beam: experimental measurements and comparison with treatment planning system calculations, RADIOTH ONC, 58(2), 2001, pp. 193-200
Citations number
15
Categorie Soggetti
Radiology ,Nuclear Medicine & Imaging","Onconogenesis & Cancer Research
Background and purpose: Dosimetric measurements and treatment planning syst
em (TPS) calculations in the region outside the clinical photon beams have
been investigated. The aim was to estimate the calculation accuracy of a sp
ecific TPS in areas that are becoming increasingly relevant with the advent
of new technologies, such as, for example, intensity modulation radiation
therapy.
Materials and methods: Measurements were performed on two different linacs
to obtain, separately, the head scatter (electrons and photons), the transm
ission below the jaws and the phantom scatter outside the primary beam for
different photon energies, distances from the field edge and field sizes. C
alculations with a commercial TPS (Helax TMS) were then obtained and compar
ed with these measurements.
Results: In general, reasonable agreement between calculations and measurem
ents was obtained (1-2%), especially for photon scattering (head and phanto
m). Nevertheless, some discrepancies were found in the electron contaminati
on computation, due probably to the approximations and assumptions made in
the TPS calculation algorithm.
Conclusions: The analyzed TPS presented good results, but for some particul
ar clinical cases and moreover for advanced techniques such as intensity mo
dulated radiation therapy, the calculation behaviour with respect to measur
ements and patient dose delivery should be carefully evaluated. (C) 2001 El
sevier Science Ireland Ltd. All rights reserved.