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Potential Benefit of Dynamic Trajectory Optimization in Radiotherapy for Different Treatment Sites

M Fix

M K Fix*, D Frei , W Volken , D Terribilini , D M Aebersold , P Manser , Division of Medical Radiation Physics and Department of Radiation Oncology, Inselspital, Bern University Hospital, and University of Bern, Switzerland


SU-I-GPD-T-507 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: Volumetric modulated arc therapy (VMAT) is a well-established treatment technique in radiotherapy using a coplanar delivery, but might be improved by dynamic couch and collimator rotations resulting in dynamic trajectory radiotherapy (DTRT). In this work the potential benefit of DTRT was investigated for several different treatment sites.

Methods: The optimization framework for DTRT was developed using the Eclipse Scripting Research Application Programming Interface (ESRAPI). The structures of the contoured target and organs at risk (OARs) are extracted using the ESRAPI. The determination of the fractional volume-overlap of the OARs with the target from potential beam directions leads to gantry-table tracks using an A* path finding algorithm. Analogously, a gantry-collimator path is determined for each gantry-table track. The resulting dynamic trajectories serve as input for the intensity modulation optimization using a research VMAT optimizer and the ESRAPI. This procedure was applied for five different clinically motivated cases: brain, head and neck, lung, esophagus and prostate. Resulting dose distributions for the standard VMAT plans and for the dynamic trajectory treatment plans were compared based on dose volume histogram (DVH) parameters.

Results: The comparison of the DVHs for the target volume showed at least the same coverage and dose homogeneity for DTRT using equal or less number of beams for all cases studied, thus leading to a potential treatment time reduction. Depending on the case, improvements in mean and maximum dose for the DTRT plans were achieved for almost all OARs compared with the VMAT plans. Improvements in mean and maximum dose were up to 50% compared to VMAT.

Conclusion: The results demonstrate that DTRT has enormous potential to reduce dose to OARs using less number of beams, while target coverage is preserved compared with VMAT treatment plans. This work was supported by Varian Medical Systems.

Funding Support, Disclosures, and Conflict of Interest: This work was supported by Varian Medical Systems.

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