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Ridge filter design and optimization for the broad‐beam three‐dimensional irradiation system for heavy‐ion radiotherapy
Author(s) -
Schaffner Barbara,
Kanai Tatsuaki,
Futami Yasuyuki,
Shimbo Munefumi,
Urakabe Eriko
Publication year - 2000
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.598934
Subject(s) - sobp , dosimetry , optics , superposition principle , homogeneity (statistics) , bragg peak , physics , beam (structure) , materials science , computational physics , mathematics , nuclear medicine , statistics , medicine , quantum mechanics
The broad‐beam three‐dimensional irradiation system under development at National Institute of Radiological Sciences (NIRS) requires a small ridge filter to spread the initially monoenergetic heavy‐ion beam to a small spread‐out Bragg peak (SOBP). A large SOBP covering the target volume is then achieved by a superposition of differently weighted and displaced small SOBPs. Two approaches were studied for the definition of a suitable ridge filter and experimental verifications were performed. Both approaches show a good agreement between the calculated and measured dose and lead to a good homogeneity of the biological dose in the target. However, the ridge filter design that produces a Gaussian‐shaped spectrum of the particle ranges was found to be more robust to small errors and uncertainties in the beam application. Furthermore, an optimization procedure for two fields was applied to compensate for the missing dose from the fragmentation tail for the case of a simple‐geometry target. The optimized biological dose distributions show that a very good homogeneity is achievable in the target.