Graduate School of Medicine, Nagoya University, 1-1-20 Daiko-minami, Higashi-ku, Nagoya, Aichi, 461-8673, Japan.
Graduate School of Medical Science, Kitasato University, 1-15-1 Kitasato, Minami, Sagamihara, Kanagawa, 252-0373, Japan.
Sci Rep. 2020 Feb 27;10(1):3572. doi: 10.1038/s41598-020-60519-z.
With advances in high-dose-rate (HDR) brachytherapy, the importance of quality assurance (QA) is increasing to ensure safe delivery of the treatment by measuring dose distribution and positioning the source with much closer intervals for highly active sources. However, conventional QA is time-consuming, involving the use of several different measurement tools. Here, we developed simple QA method for HDR brachytherapy based on the imaging of Cherenkov emission and evaluated its performance. Light emission from pure water irradiated by an Ir γ-ray source was captured using a charge-coupled device camera. Monte Carlo calculations showed that the observed light was primarily Cherenkov emissions produced by Compton-scattered electrons from the γ-rays. The uncorrected Cherenkov light distribution, which was 5% on average except near the source (within 7 mm from the centre), agreed with the dose distribution calculated using the treatment planning system. The accuracy was attributed to isotropic radiation and short-range Compton electrons. The source positional interval, as measured from the light images, was comparable to the expected intervals, yielding spatial resolution similar to that permitted by conventional film measurements. The method should be highly suitable for quick and easy QA investigations of HDR brachytherapy as it allows simultaneous measurements of dose distribution, source strength, and source position using a single image.
随着高剂量率 (HDR) 近距离放射治疗的发展，为了确保治疗的安全实施，需要更加频繁地测量剂量分布并更紧密地定位放射源，因此质量保证 (QA) 的重要性日益增加。然而，传统的 QA 方法非常耗时，需要使用多种不同的测量工具。在这里，我们开发了一种基于切伦科夫发射成像的 HDR 近距离放射治疗简单 QA 方法，并评估了其性能。使用电荷耦合器件 (CCD) 相机捕获纯水中的 Ir γ 射线源辐照产生的光发射。蒙特卡罗计算表明，观察到的光是主要由γ射线的康普顿散射电子产生的切伦科夫发射。未经校正的切伦科夫光分布在离源 7mm 以内（中心附近）平均为 5%，与使用治疗计划系统计算的剂量分布一致。这种准确性归因于各向同性辐射和短程康普顿电子。从光图像测量的源位置间隔与预期间隔相当，产生类似于传统胶片测量允许的空间分辨率。该方法非常适合快速简便地进行 HDR 近距离放射治疗的 QA 研究，因为它允许使用单个图像同时测量剂量分布、源强度和源位置。
