Jens Wölfelschneider1, Thomas Friedrich2, Robert Lüchtenborg2, Klemens Zink3, Michael Scholz2, Lei Dong4, Marco Durante5, Christoph Bert6. 1. GSI - Helmholtz Centre for Heavy Ion Research, Department of Biophysics, Darmstadt, Germany; TH Mittelhessen, Department of Hospital and Medical Engineering, Environmental Technology and Biotechnology, Giessen, Germany; University Hospital Erlangen and Friedrich-Alexander-Universität Erlangen-Nürnberg, Radiation Oncology, Germany. Electronic address: jens.woelfelschneider@fau.de. 2. GSI - Helmholtz Centre for Heavy Ion Research, Department of Biophysics, Darmstadt, Germany. 3. TH Mittelhessen, Department of Hospital and Medical Engineering, Environmental Technology and Biotechnology, Giessen, Germany; University Hospital Giessen-Marburg, Department of Radiotherapy and Radiooncology, Germany. 4. The University of Texas MD Anderson Cancer Center, Department of Radiation Physics, Houston, United States. 5. GSI - Helmholtz Centre for Heavy Ion Research, Department of Biophysics, Darmstadt, Germany; TU Darmstadt, Department of Condensed Matter Physics, Darmstadt, Germany. 6. GSI - Helmholtz Centre for Heavy Ion Research, Department of Biophysics, Darmstadt, Germany; University Hospital Erlangen and Friedrich-Alexander-Universität Erlangen-Nürnberg, Radiation Oncology, Germany.
Abstract
BACKGROUND AND PURPOSE: Scanned particle beam therapy may result in over and under dosages within the target volume. This study quantifies how CTV dose coverage improves with number of fractions and fields. MATERIALS AND METHODS: Based on 4DCTs of nine lung tumor patients, treatment plans were optimized separately for four different fields using an ITV approach. 4D RBE-weighted dose distributions were calculated for varying motion parameters and fraction numbers. The total RBE-weighted dose was determined for one and four-field application per fraction. DVHs were analyzed for the tumor and interpreted based on statistical modeling. RESULTS: Dose homogeneity within the CTV increased with the fraction number, but depends significantly on the tumor motion amplitude. For single-field schedules and amplitudes >6mm, the dose coverage indices (V95min=90.7% and V107max=0.4%) differed to the stationary case even after 40 fractions. Target coverage for a four-field approach followed a proposed model and homogeneous dose distributions could be achieved 6-times faster than single-field treatments. CONCLUSIONS: Fractionated delivery improves dose homogeneity in scanned ion beam therapy of moving targets. The achievable homogeneity depends mainly on tumor volume and motion amplitude. The outcome of multiple-field irradiations can be predicted based on single-field results and accelerates the achievement of homogeneous dose distributions.
BACKGROUND AND PURPOSE: Scanned particle beam therapy may result in over and under dosages within the target volume. This study quantifies how CTV dose coverage improves with number of fractions and fields. MATERIALS AND METHODS: Based on 4DCTs of nine lung tumorpatients, treatment plans were optimized separately for four different fields using an ITV approach. 4D RBE-weighted dose distributions were calculated for varying motion parameters and fraction numbers. The total RBE-weighted dose was determined for one and four-field application per fraction. DVHs were analyzed for the tumor and interpreted based on statistical modeling. RESULTS: Dose homogeneity within the CTV increased with the fraction number, but depends significantly on the tumor motion amplitude. For single-field schedules and amplitudes >6mm, the dose coverage indices (V95min=90.7% and V107max=0.4%) differed to the stationary case even after 40 fractions. Target coverage for a four-field approach followed a proposed model and homogeneous dose distributions could be achieved 6-times faster than single-field treatments. CONCLUSIONS: Fractionated delivery improves dose homogeneity in scanned ion beam therapy of moving targets. The achievable homogeneity depends mainly on tumor volume and motion amplitude. The outcome of multiple-field irradiations can be predicted based on single-field results and accelerates the achievement of homogeneous dose distributions.
Authors: Suliana Teoh; Ben George; Francesca Fiorini; Katherine A Vallis; Frank Van den Heuvel Journal: Br J Radiol Date: 2020-02-04 Impact factor: 3.629