Program Information
Development of a Ripple Filter with Honeycomb Pattern for Proton Line Scanning
N Kamiguchi*, Y Aoki , K Sasai , T Miyashita , Y Mikami , Sumitomo Heavy Industries, Ltd., Tokyo
Presentations
SU-I-GPD-T-202 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose: Modulated scanning method is getting to be standard method but this method is recognized as a slow irradiation method in condition that the tumor locates shallow part. It takes time further more as sharp peak at low energy proton requires enormous energy layers to deliver the dose.To apply scanning method to moving target, the dose should be delivered in short time.Ripple filter is one of the methods to solve this matter which can decrease the number of energy layers by shuffling the beam energy of incident proton and broadening the peak shape of Bragg curve.
Methods: We designed some ripple filters which spread out 70 MeV Bragg curve to high energies peak. The structure of range modulator units is like an array of pyramids that each unit bonds with next units allocated in the reticular or honeycomb pattern. There is blank space in the patterns to achieve scatter-less equipment because low energy proton can be easily scattered. To confirm the feasibility of this structure and the calculation accuracy, we created the test pieces of each ripple filter. As performance test, we measured IDD curve and lateral profile for spot beam.
Results: We could manufacture the filters which have area of 170mm diameter without any cracks. We confirmed the validity of the design because measurement results got consistency with calculated curve shape. And also we confirmed pitch of the modulator units was fine enough to prevent the filter structure from affecting lateral spot shape with 1.5mm pitch because lateral beam shape was symmetry and had almost Gaussian shape.
Conclusion: We are developing some ripple filters to shorten irradiation time. We created the ripple filters with honeycomb structure and conducted the performance test.
Funding Support, Disclosures, and Conflict of Interest: All authers are employees of Sumitomo Heavy Industries, Ltd.
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