Moskvin Vadim P, Estabrook Neil C, Cheng Chee-Wai, Das Indra J, Johnstone Peter A S
Department of Radiation Oncology, Indiana University School of Medicine, Indianapolis, IN, USA IU Health Proton Therapy Center, Bloomington, IN, USA 535 Barnhill Dr., RT-041, Indianapolis, IN 46202, USA
Department of Radiation Oncology, Indiana University School of Medicine, Indianapolis, IN, USA IU Health Proton Therapy Center, Bloomington, IN, USA 535 Barnhill Dr., RT-041, Indianapolis, IN 46202, USA.
Technol Cancer Res Treat. 2015 Oct;14(5):643-52. doi: 10.7785/tcrt.2012.500435. Epub 2014 Nov 26.
Proton beam delivery technology is under development to minimize the scanning spot size for uniform dose to target, but it is also known that the superficial dose could be as high as the dose at Bragg peak for narrow and small proton beams. The objective of this study is to explore the characteristics of dose distribution at shallow depths using Monte Carlo simulation with the FLUKA code for uniform scanning (US) and discrete spot scanning (DSS) proton beams. The results show that the superficial dose for DSS is relatively high compared to US. Additionally, DSS delivers a highly heterogeneous dose to the irradiated surface for comparable doses at Bragg peak. Our simulation shows that the superficial dose can become as high as the Bragg peak when the diameter of the proton beam is reduced. This may compromise the advantage of proton beam therapy for sparing normal tissue, making skin dose a limiting factor for the clinical use of DSS. Finally, the clinical advantage of DSS may not be essential for treating uniform dose across a large target, as in craniospinal irradiation (CSI).
质子束传输技术正在研发中，目的是将扫描光斑尺寸最小化，以便向靶区提供均匀剂量，但众所周知，对于窄小质子束，表面剂量可能高达布拉格峰处的剂量。本研究的目的是使用FLUKA代码通过蒙特卡罗模拟，探索均匀扫描（US）质子束和离散点扫描（DSS）质子束在浅深度处的剂量分布特征。结果表明，与US相比，DSS的表面剂量相对较高。此外，对于布拉格峰处相当的剂量，DSS向受照表面提供的剂量高度不均匀。我们的模拟表明，当质子束直径减小时，表面剂量可能会高达布拉格峰。这可能会损害质子束治疗在 sparing正常组织方面的优势，使皮肤剂量成为DSS临床应用的限制因素。最后，DSS的临床优势对于像全脑全脊髓照射（CSI）那样在大靶区内治疗均匀剂量可能并非至关重要。
