gms | German Medical Science

48th Meeting of the Particle Therapy Co-Operative Group

Particle Therapy Co-Operative Group (PTCOG)

28.09. - 03.10.2009, Heidelberg

Incorporation of Gaussian beam splitting into the grid dose spreading algorithm for radiotherapy with heavy charged particles

Meeting Abstract

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  • N. Kanematsu - Department of Accelerator and Medical Physics, National Institute of Radiological Sciences, Chiba, Japan

PTCOG 48. Meeting of the Particle Therapy Co-Operative Group. Heidelberg, 28.09.-03.10.2009. Düsseldorf: German Medical Science GMS Publishing House; 2009. Doc09ptcog105

DOI: 10.3205/09ptcog105, URN: urn:nbn:de:0183-09ptcog1058

Published: September 24, 2009

© 2009 Kanematsu.
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Outline

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Purpose: To achieve accurate and fast dose calculation for radiotherapy with protons and ions, this work aims to formulate an algorithm that incorporates recently proposed beam-modeling and kernel-convolution techniques, beam splitting and grid dose spreading.

Methods: The beam splitting method was implemented into the beam-transport part of the grid-dose-spreading algorithm. Interplay between the beam and grid structures causes artifactual dose fluctuation for the grid-dose-spreading algorithm of interaction point of view, against which an anti-quantization technique, intervoxel beam sharing, was developed. Against problems with angled incidence, beam splitting itself and an alternative and more natural approach, grid normalization, were investigated. The effectiveness of these computational techniques was evaluated with proton and carbon-ion beam models in pencil-beam and broad-beam configurations.

Results: Implementation of beam splitting enabled to handle fine structure of density heterogeneity within a spread of an incident beam. The intervoxel beam sharing resolved artifactual dose fluctuation of the order of 10% in our case. For angled incidence, the beam splitting improved kernel deformation but yielded another artifactual dose fluctuation of the same order. The grid normalization resolved these problems without significant loss of information nor loss of speed. Separation between beam transport and kernel convolution in the grid dose spreading algorithm minimized the impact of multiplication of split beams on the computing time.

Conclusions: The grid dose spreading algorithm was extended to incorporate techniques of grid normalization, intervoxel beam sharing, and beam splitting. The resultant algorithm is free of the artifacts from beam-grid interplay and efficiently addresses the overreach and detour effects in dose calculation of proton and ion beams.