München 2009 – wissenschaftliches Programm
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ST: Fachverband Strahlen- und Medizinphysik
ST 7: Ion Radiation Therapy 2: Target Motion Management
ST 7.2: Vortrag
Mittwoch, 11. März 2009, 15:45–16:00, A021
Compensation of dose changes due to intrafractional tumor motion — •Robert Lüchtenborg1, Nami Saito1, Naved Chaudhri1, Marco Durante1, Eike Rietzel1,2, and Christoph Bert1 — 1GSI Biophysik, Darmstadt — 2Siemens Healthcare Sector, Workflow & Solutions, Particle Therapy, Erlangen
Treating tumors that are subject to intrafractional motion with scanned ion beams leads to deterioration of the deposited dose pattern. Thus techniques to mitigate motion effects are currently investigated. The most favorable among them in terms of target conformity and sparing of organs at risk is tracking, i.e. individually adapting Bragg peak positions to the changing tumor position.
While the main part of dose delivered by an ion pencil beam is deposited at the Bragg peak position some dose is delivered in the plateau before the Bragg peak. These dose contributions can be considered in treatment planning for stationary tumors but are subject to unpredictable changes in case of intrafractional tumor motion.
When tracking is used motion induced changes in dose deposition to the plateau region have to be considered. That means not only the position but also the particle number of each ion beamlet has to be adapted. Because the adaptation values depend on the a priori not exactly known trajectory (e.g. breathing period of patient changes) they have to be determined during treatment delivery.
Functionality to compensate for motion induced dose changes has been implemented to the beam tracking system at GSI and first experimental results will be presented.