Author: Jenghwa Chang, Chingyun Cheng, J Isabelle Choi, Muhammad Hamza, Minglei Kang, Tyler Kaulfers, Grant Lattery, Haibo Lin, Charles B. Simone, Xingyi Zhao 👨🔬
Affiliation: Peking University, Hofstra University Medical Physics Program, New York Proton Center, Department of Human Oncology, University of Wisconsin School of Medicine and Public Health, Physics and Astronomy, Hofstra University, Physics Resident at Montefiore Einstein, Department of Human Oncology, University of Wisconsin-Madison 🌍
Purpose: In terms of high dose rate FLASH, the question remains on how to properly deliver treatment and what clinical sites are feasible to deliver such treatment. The novel Bragg peak (BP-FLASH) and mini ridge filter(mRF) are two solutions potentially for clinical application due to the capacity in achieving highly conformal dose. This study investigates the clinical feasibility and dosimetric results of the BP-FLASH and mRF methods for both breast and prostate patients.
Methods: 10 breast patients and 10 prostate patients(20 total) that were treated with
conventional proton pencil beam scanning(PBS) at the New York Proton Center(NYPC)
were retrospectively replanned for FLASH and FLASH miniRF treatments. They were planned at 40Gy in 5 fractions(8Gy/fx) on a 250MV beam, with the FLASH methods being normalizd to 95%. A prior study was conducted to just compare the conventional treatment to the
FLASH technique with proper implementation of the necessary devices within the TPS
only being discussed. A BP-FLASH model using Ray Tracing methods calculated the beam specific range compensators (RC) and range shifters (RS) thickness. A miniRF, range compensator and biological factors have all been added for a more realistic representation of what this novel delivery method looks like.
Results: Conventional PBS, FLASH and filter FLASH all met CTV metrics. The dmax for rectum and bladder are 3433.29cGy and 4401.0cGy for BP-FLASH, and 3569.5cGy amd 4203.5cGy for mRF FLASH. The mean dose to heart, D2cc to left breast, and left lung V20Gy, are .4%, 109.3%, 1.6%, for BP-FLASH, and .5%, 102.4%, 1.7% for mRF FLASH.
Conclusion: Plans were able to achieve comparable plan quality between Mini Ridge
Filter, Bragg Peak FLASH and Conventional proton therapy, despit som organs having an increasd dmax. The results show clinical
feasibility for the use and implementation of miniRF FLASH.