Berlin 2008 – wissenschaftliches Programm

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ST: Fachverband Strahlen- und Medizinphysik

ST 5: Heavy Ion Therapy and Related Basic Research I

ST 5.3: Vortrag

Dienstag, 26. Februar 2008, 10:00–10:15, H 2033

Tracking, gating, and rescanning as motion mitigation techniques in carbon ion therapy — •Christoph Bert¹, Alexander Schmidt¹, Nami Saito¹, Naved Chaudhri¹, Dieter Schardt¹, and Eike Rietzel^1,2 — ¹GSI, Planckstr. 1, 64291 Darmstadt — ²Siemens Medical Solutions, Hofmannstr. 26, 91052 Erlangen

Target motion in tumor therapy with scanned ion beams causes dose deterioration if no mitigation techniques are used. At Gesellschaft für Schwerionenforschung (GSI) raster scanned carbon beams are used for tumor therapy. Currently treatment is limited to sites in the head, neck, and pelvis but we are investigating rescanning, gating, and tracking as mitigation techniques for moving targets.

Rescanning mitigates the influence of motion because the treatment plan is applied multiple times. On average this leads to homogeneous coverage of the target if margins cover the motion amplitude. With gating the irradiation is restricted to parts of the motion cycle. The reduced motion amplitude results in less interplay and reduced margins. Target coverage can be achieved if the overlap of pencil beam positions is aligned to the residual motion amplitude. For tracking target motion is compensated by adapting the Bragg peak position laterally as well as longitudinally in depth. In principle, no margins or increased pencil beam overlap are necessary.

At GSI we focus on tracking because this technique results in minimum dose to normal tissue. Nevertheless, we implemented all mitigation techniques to allow comparisons. An overview of experimental results will be presented.