Program Information
Beam Angle Optimization Incorporating Anatomical Heterogeneities for Pencil Beam Scanning Charged-Particle Therapy
C Toramatsu*, T Inaniwa , National Institute of Radiological SciencesChiba
Presentations
TH-CD-209-2 (Thursday, August 4, 2016) 10:00 AM - 12:00 PM Room: 209
Purpose:
In charged particle therapy with pencil beam scanning (PBS), localization of the dose in the Bragg peak makes dose distributions sensitive to lateral tissue heterogeneities. Sensitivity of a PBS plan to lateral tissue heterogeneity can be reduced by selecting suitable beam angles. The purpose of this study is to establish a fast and accurate method of beam angle selection for PBS.
Methods:
The lateral tissue heterogeneity surrounding the path of respective pencil beams at a given angle was quantified with the heterogeneity number using effective density data of patients. To shorten the computation time, one dimensional dose calculation and optimization were conducted along the central axis of pencil beams originating from the scanning magnets. Calculation was performed for all fields with possible gantry and couch angles. The angles leading the minimum mean heterogeneity number was selected as the optimal beam angle. Three head and neck (H&N) cancer patients were used to evaluate our method. Dose distributions and their robustness to range and set up errors were evaluated for all tested angles, and their relation to their heterogeneity numbers were investigated.
Results:
Variety of heterogeneity number was clearly shown due to air cavities and bony structures in the patients. The mean value of heterogeneity number in all possible fields varied between 1.2 and 10.6 mm. By selecting a field with a lower mean value of heterogeneity number, target dose coverage and robustness of the fields were improved.
Conclusion:
We developed a computational method to determine a beam angle that leads good target coverage and robustness to setup errors. The developed stand-alone computation program is simple, fast, accurate and applicable for beam angle selection in PBS therapy.
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