Program Information
Dosimetric Analysis of Optimum Non-Collisional Trajectory Modulated Arc Deliveries for Intracranial Lesions Under Conventional C-Arm Linac Phase Space Geometry
S Khan1*, E Chin2 , L Xing3 , D Hristov4 , B Fahimian5 , (1) Stanford Univ School of Medicine, Palo Alto, California, (2) BCCA- Vancouver Island Centre, Victoria, BC, (3) Stanford Univ School of Medicine, Stanford, CA, (4) Stanford University School of Medicine, Palo Alto, CA, (5) Stanford University School of Medicine, Stanford, CA
Presentations
WE-RAM3-GePD-T-3 (Wednesday, August 2, 2017) 10:30 AM - 11:00 AM Room: Therapy ePoster Lounge
Purpose: Development of a class-based optimized trajectory for cranial tumors through incorporation dynamic trajectory modulated coplanar and non-coplanar arcs on conventional C-arm linacs phase space via comparative dosimetric assessment of VMAT and Trajectory Modulated Arc Therapy (TMAT).
Methods: In order to explore the full-scale of arc delivery beyond the limitations of VMAT, a Trajectory Modulated Arc Therapy (TMAT) technique is designed for the treatments of intracranial tumors by incorporating dynamic couch motion. The treatment planning platform, based on the generalized form of direct aperture optimization, was developed in MATLAB to optimize dynamic MLC apertures and associated cumulative beam-on times. Depending upon the tumor location, optimized TMAT trajectories were designed using the combinations of Non-coplanar (coronal & sagittal) and Coplanar (axial) arcs. TMAT planning results were then retrospectively compared to VMAT plans within the same optimization environment.
Results: TMAT study of 10 patients with tumors of different sizes (varying from 5 cm3 to 266 cm3), distinct shapes and in various regions of the skull, is performed. Study shows a reduction in mean dose to many critical organs such as brainstem (25%), cochlea (31%) and optic nerve (40%) when compared to VMAT while maintaining the mean dose to PTV. Conformity Index analysis also shows that dose conformity to target volume improves by 10% for some of the cases as compared to VMAT. Delivery efficiency study by using Developer Mode of TrueBeam suggests that these trajectories are deliverable and their delivery time is comparable to VMAT with a maximum time difference of 50 seconds
Conclusion: Incorporation of non-coplanar coronal arc arrangements in TMAT planning system not only helps to design an optimized trajectory for intracranial tumors but also enhances the dose conformity to PTV. Furthermore, the sparing of the surrounding critical organs also improves when compared with VMAT planning technique.
Funding Support, Disclosures, and Conflict of Interest: This research was partially supported by a research grant from Varian Medical Systems
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