Article
Beam model used in treatment planning for carbon-ion scanning with range shifter plates
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Published: | September 24, 2009 |
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In order to use an intensity-controlled raster scan method at the new treatment facility in HIMAC, we have developed a code system dedicated to the planning of radiotherapy with the scanned 12C beam. In the code, the lateral dose distributions of the pencil beam has been expressed by a single Gaussian with the spread depending on the depth and the thickness of the range shifter plate. The effect of the beam spread due to multiple scattering in the range shifter plates can be included in this model, at least for the primary particles. However, our recent research revealed that the large-angle scattered fragments affect the dose far away from the track of the primary particles and make the doses within the target volume dependent on the field size. In order to account for the observed dependencies, we proposed to express the lateral dose distribution of the scanned carbon beam by sum of three Gaussians. In the meeting, the detailed explanations of the model and the experimental results with it will be shown, in addition to the current status of the development of the treatment planning code.