Monte Carlo-based treatment planning for a spoiler system with experimental validation using plane-parallel ionization chambers.
A beam spoiler is often used to increase the build-up dose near the surface for treatment of superficial treatment areas. Photon-beam spoilers produce a large amount of contaminant electrons, conditions for which standard, commercial treatment-planning system dose-calculation algorithms are inadequate for producing accurate dose calculations. In this study, we implemented a Monte Carlo (MC) dose-calculation algorithm for this spoiler system. With and without a spoiler of 1 cm Lucite, depth doses and transverse profiles in the build-up region were measured for field sizes of 5 x 5 cm2 and 10 x 10 cm2 at the spoiler-to-surface distances (STSDs) of 6, 10 and 15 cm. An Attix chamber and a Markus chamber were used for depth doses, whereas a diode detector was used for transverse profiles. An MC simulation using BEAM/DOSXYZ was used to compare the calculated and the measured data. The MC calculations agreed with the Attix chamber measurements within 2% for all STSDs and field sizes, whereas the Markus data--even with corrections made-showed a discrepancy of about 3.5% with a maximum difference of 7.3% for a field size of 10 x 10 cm2 at an STSD of 6 cm. The MC treatment-planning system was successfully applied to a head-and-neck case using 6 MV photon beams with a beam spoiler.
Kang
Sei-Kwon
SK
Department of Radiation Oncology, Hallym University Sacred Heart Hospital, Anyang, Korea.
Cho
Byung Chul
BC
Park
Sung Ho
SH
Park
Hee Chul
HC
Bae
HoonSik
H
Kim
Jong Oh
JO
Keall
Paul J
PJ
Siebers
Jeffrey V
JV
D000465:Algorithms; D004583:Electrons; D006258:Head and Neck Neoplasms / Q000532:radiotherapy; D006801:Humans; D007477:Ions; D009010:Monte Carlo Method; D010315:Particle Accelerators; D017785:Photons; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000379:methods; D012984:Software; D014867:Water
D007477:Ions; D014867:Water