Heidelberg 2006 – scientific programme
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ST: Strahlen- und Medizinphysik
ST 7: Strahlentherapie mit schnellen Ionen II
ST 7.3: Talk
Tuesday, March 14, 2006, 11:50–12:00, D
CT calibration for Heavy-ion treatment planning at the DKFZ — •Sima Qamhiye1, Malte Ellerbrock 1, Dieter Schardt2, and Oliver Jäkel1 — 1German Cancer Research Center (DKFZ) - Heidelberg — 2Gesellschaft für Schwerionenforschung (GSI) - Darmstadt
The uncertainty of ion-range in Carbon-therapy is mainly related to the electron density of the irradiated tissues. CT-numbers (HU) are the only indication to electron density with reasonable spatial resolution. Therefore, a calibration between ion range and HU is required to accurately calculate Carbon-range in tissue. The empirical calibration currently used for treatment planning at the GSI facility allows spatial accuracy up to 2-3 mm of Carbon range in head or neck tumors. In this work, the CT-calibration techniques currently used in the DKFZ to obtain a HU- ion range empirical calibration is presented. Gammex electron density substitutes and fresh tissue were cleaned and stacked in Plexiglas containers for both water equivalent path length (WEPL) and CT measurements. substitute measurements were used to obtain the empirical calibration curve of the CT in question while tissue measurements were used to estimate the quality of the calibration curve and the dependent range calculation. Substitutes used for CT-calibration should be carefully chosen but tissue measurements should be used to check the accuracy of empirical calibration. Tissue measurements show a good agreement with the calibration curves developed for different CT machines, maximum deviation 5%.