Comparative Clinical Pencil Beam Scanned Proton Flash Therapy: Transmission Beams Vs. Range Stopping Beams
J Farr1,2*, A Kolano1,2, T Gray3, C Liu3, P Xia3, (1) Applications of Detectors and Accelerators to Medicine (ADAM) SA, Meyrin, Switzerland, (2) Advanced Oncotherapy plc, London, UK, (3) The Cleveland Clinic Foundation, Cleveland, OH
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PO-GePV-T-153 (Sunday, 7/10/2022) [Eastern Time (GMT-4)]
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Purpose: To investigate the proton flash physical treatment quality between two different clinical delivery modalities: scanned proton beams that exit the patient, Transmission Beams (TBs) in comparison to scanned proton stopping beams (SBs) that range out the target within the patient.
Methods: A proton cyclotron and linac were modeled in a commercial treatment planning system (TPS). Lung, brain, and prostate cases were planned with Intensity Modulated Proton Therapy (IMPT) using the TPS for TBs and SBs. As the base case, both the TB and SB IMPT plans were not optimized for Average Dose Rate (DRave). Subsequently, DRave optimized IMPT plans were produced using the dose specification function with upscaled spot and energy layer spacing. The base and DRave optimized TB, and SB plans were compared in the TPS for integral dose, dose to Organs at Risk (OARs), and DRave to provide field deliveries in less than 0.5 seconds.
Results: Because cyclotrons take more than 0.5 seconds for an energy change, they were limited to TB deliveries. The proton linac changes the energy in 0.005 seconds; hence, flash TBs and SBs were possible for the planned cases. Integral and OAR doses are lowest across all instances for the proton linac SB plans. On average, the DRave is 90 Gy/s for the cyclotron TB plans, 60 Gy/s for the linac TB plans, 56 Gy/s for the linac SB plans.
Conclusion: SB flash plans offer the advantage over TB flash plans of higher physical dose conformity. SB flash plans require ultra-fast energy changes and broader spot and energy layer spacing than non-flash IMPT plans. TB and SB flash plans were achievable for a cyclotron and a linac. Only the proton linac can produce scanned SB plans without the need for additional beam modifying devices. The study reports results on a physical dose basis.
Funding Support, Disclosures, and Conflict of Interest: Jonathan Farr holds a senior management position at ADAM SA, Meyrin, Switzerland and is a shareholder in Advanced Oncotherapy (AVO), plc, London, UK. Anna-Maria Kolano is an employee of ADAM SA and participates in the employee share option program of AVO. Ping Xia receives research funding support from AVO.
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