Department of Radiation Oncology, Linkou Chang Gung Memorial Hospital, Taoyuan City, Taiwan (R.O.C).
Department of Biomedical Imaging and Radiological Sciences, National Yang Ming Chiao Tung University, Taipei City, Taiwan (R.O.C).
J Appl Clin Med Phys. 2024 Jul;25(7):e14362. doi: 10.1002/acm2.14362. Epub 2024 Apr 26.
Proton stereotactic radiosurgery (PSRS) has emerged as an innovative proton therapy modality aimed at achieving precise dose delivery with minimal impact on healthy tissues. This study explores the dosimetric outcomes of PSRS in comparison to traditional intensity-modulated proton therapy (IMPT) by focusing on cases with small target volumes. A custom-made aperture system designed for proton therapy, specifically tailored to small target volumes, was developed and implemented for this investigation.
A prerequisite mechanical validation through an isocentricity test precedes dosimetric assessments, ensuring the seamless integration of mechanical and dosimetry analyses. Five patients were enrolled in the study, including two with choroid melanoma and three with arteriovenous malformations (AVM). Two treatment plans were meticulously executed for each patient, one utilizing a collimated aperture and the other without. Both plans were subjected to robust optimization, maintaining identical beam arrangements and consistent optimization parameters to account for setup errors of 2 mm and range uncertainties of 3.5%. Plan evaluation metrics encompassing the Heterogeneity Index (HI), Paddick Conformity Index (CI), Gradient Index (GI), and the R50% index to evaluate alterations in low-dose volume distribution.
The comparative analysis between PSRS and traditional PBS treatment revealed no significant differences in plan outcomes, with both modalities demonstrating comparable target coverage. However, collimated apertures resulted in discernible improvements in dose conformity, dose fall-off, and reduced low-dose volume.
This study underscores the advantageous impact of the aperture system on proton therapy, particularly in cases involving small target volumes.
质子立体定向放射外科（PSRS）作为一种创新的质子治疗方式，旨在实现精确的剂量递送，同时对健康组织的影响最小。本研究通过关注小靶区体积的病例，比较了 PSRS 与传统强度调制质子治疗（IMPT）的剂量学结果。为此研究开发并实施了一种专门为质子治疗设计的定制孔径系统，特别适用于小靶区体积。
在进行剂量学评估之前，需要进行等中心性测试的机械验证，以确保机械和剂量学分析的无缝集成。本研究纳入了 5 名患者，其中 2 名患有脉络膜黑色素瘤，3 名患有动静脉畸形（AVM）。为每位患者精心制定了两种治疗计划，一种使用准直孔径，另一种则不使用。两种计划都经过了强大的优化，保持相同的光束排列和一致的优化参数，以考虑 2mm 的设置误差和 3.5%的范围不确定性。评估指标包括不均匀性指数（HI）、Paddick 适形指数（CI）、梯度指数（GI）和 R50%指数，以评估低剂量体积分布的变化。
PSRS 与传统 PBS 治疗的比较分析表明，计划结果没有显著差异，两种方法均能实现相似的靶区覆盖。然而，准直孔径可明显改善剂量适形性、剂量下降和减少低剂量体积。
本研究强调了孔径系统对质子治疗的有利影响，特别是在涉及小靶区体积的情况下。
