Yin Lingshu, Masumi Umezawa, Ota Kan, Sforza Daniel M, Miles Devin, Rezaee Mohammad, Wong John W, Jia Xun, Li Heng
Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Hitachi, Ltd., Research and Development Group, Center for Technology Innovation-Energy, 7-2-1, Omika-chou, Hitachi-shi 319-1292, Ibaraki-ken, Japan.
Cancers (Basel). 2024 Jan 3;16(1):221. doi: 10.3390/cancers16010221.
This study aims to present the feasibility of developing a synchrotron-based proton ultra-high dose rate (UHDR) pencil beam scanning (PBS) system.
The RF extraction power in the synchrotron system was increased to generate 142.4 MeV pulsed proton beams for UHDR irradiation at ~100 nA beam current. The charge per spill was measured using a Faraday cup. The spill length and microscopic time structure of each spill was measured with a 2D strip transmission ion chamber. The measured UHDR beam fluence was used to derive the spot dwell time for pencil beam scanning. Absolute dose distributions at various depths and spot spacings were measured using Gafchromic films in a solid-water phantom.
For proton UHDR beams at 142.4 MeV, the maximum charge per spill is 4.96 ± 0.10 nC with a maximum spill length of 50 ms. This translates to an average beam current of approximately 100 nA during each spill. Using a 2 × 2 spot delivery pattern, the delivered dose per spill at 5 cm and 13.5 cm depth is 36.3 Gy (726.3 Gy/s) and 56.2 Gy (1124.0 Gy/s), respectively.
The synchrotron-based proton therapy system has the capability to deliver pulsed proton UHDR PBS beams. The maximum deliverable dose and field size per pulse are limited by the spill length and extraction charge.
本研究旨在探讨开发基于同步加速器的质子超高剂量率（UHDR）笔形束扫描（PBS）系统的可行性。
提高同步加速器系统中的射频提取功率，以产生142.4 MeV的脉冲质子束，用于在约100 nA束流的情况下进行UHDR照射。使用法拉第杯测量每次溢出的电荷量。用二维条带传输电离室测量每次溢出的溢出长度和微观时间结构。测量得到的UHDR束流注量用于推导笔形束扫描的束斑驻留时间。在固体水模体中使用加氟显色胶片测量不同深度和束斑间距处的绝对剂量分布。
对于142.4 MeV的质子UHDR束，每次溢出的最大电荷量为4.96±0.10 nC，最大溢出长度为50 ms。这意味着每次溢出期间的平均束流约为100 nA。采用2×2束斑投递模式时，在5 cm和13.5 cm深度处每次溢出的投递剂量分别为36.3 Gy（726.3 Gy/s）和56.2 Gy（1124.0 Gy/s）。
基于同步加速器的质子治疗系统有能力递送脉冲质子UHDR PBS束。每个脉冲的最大可递送剂量和射野大小受溢出长度和提取电荷量的限制。
