Ridge Filter Design For a Particle Therapy Line

다국어 초록 (Multilingual Abstract)

The beam irradiation system for particle therapy can use a passive or an active beam irradiationmethod. In the case of an active beam irradiation, using a ridge filter would be appropriate togenerate a spread-out Bragg peak (SOBP) through a large scanning area. For this study, a ridgefilter was designed as an energy modulation device for a prototype active scanning system at MC-50in Korea Institute of Radiological And Medical Science (KIRAMS). The ridge filter was designed tocreate a 10 mm of SOBP for a 45-MeV proton beam. To reduce the distal penumbra and the initialdose, [DM] determined the weighting factor for Bragg Peak by applying an in-house iteration codeand the Minuit Fit package of Root. A single ridge bar shape and its corresponding thickness wereobtained through 21 weighting factors. Also, a ridge filter was fabricated to cover a large scanningarea (300 × 300 mm2) by Polymethyl Methacrylate (PMMA). The fabricated ridge filter was testedat the prototype active beamline of MC-50. The SOBP and the incident beam distribution wereobtained by using HD-810 GaF chromatic film placed at a right triangle to the PMMA block. Thedepth dose profile for the SOBP can be obtained precisely by using the flat field correction andmeasuring the 2-dimensional distribution of the incoming beam. After the flat field correction isused, the experimental results show that the SOBP region matches with design requirement well,with 0.62% uniformity.

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