Department of Radiation Oncology, Stanford University, Stanford, CA 94305, United States of America.
equal contribution.
Phys Med Biol. 2020 Nov 17;65(22):225005. doi: 10.1088/1361-6560/abb570.
The purpose of this study is to leverage radioluminescence imaging for the development of an automated high-dose-rate (HDR) brachytherapy quality assurance (QA) system that enables simultaneous measurements of dwell position, dwell time, wire velocity, and relative source strength in a single test. The system consists of a radioluminescence phosphor sheet (a mixture of GdOS:Tb and PDMS) positioned atop a HDR needle applicator, a complementary metal-oxide-semiconductor digital camera used to capture the emitted radioluminescence signals from the scintillator sheet, and an in-house graphical user interface for signal processing. The signal processing was used to extract source intensity, location, and elapsed time, yielding the final measurements on dwell position, dwell time, and wire velocity. The source strength relative to the well chamber calibration (in unit of Air-Kerma strength, S ) is measured by establishing a calibration curve that correlates S with the detector response. Validation experiments are performed using three customized treatment plans. With these plans, the dwell position and dwell time are verified for a range of 110.0 cm-117.5 cm and 2 s-16 s, respectively, and the linear correlation with S is demonstrated for the source strength varying between 28 348 U (cGy cm h) and 41 906 U. The wire velocity, i.e. the speed of the radioactive source averaged over the distance in between dwell positions, is calculated for various distances ranging from 5 mm to 50 mm. Results show that the mean deviations of the measured dwell position and dwell time are 0.1 mm (range from 0 to 0.2 mm) and 32.5 ms (range from 0 to 60.0 ms) with respect to the planned values, respectively, and the system response is highly linear with S ( R = 0.998). Moreover, the measured wire velocities are comparable to previously reported values. Benefitting from the compact hardware design and image processing algorithms, the system provides a practical, reliable, and comprehensive solution for HDR QA.
本研究旨在利用放射发光成像开发一种自动化高剂量率（HDR）近距离治疗质量保证（QA）系统，该系统能够在单次测试中同时测量驻留位置、驻留时间、线速度和相对源强度。该系统由位于 HDR 针状施源器上方的放射发光磷光体片（GdOS:Tb 和 PDMS 的混合物）、用于捕获闪烁体片发射的放射发光信号的互补金属氧化物半导体数字相机以及用于信号处理的内部图形用户界面组成。该信号处理用于提取源强度、位置和经过的时间，从而得出驻留位置、驻留时间和线速度的最终测量结果。源强度与井室校准的相对关系（以空气比释动能强度，S 为单位）是通过建立与探测器响应相关的 S 校准曲线来测量的。通过三个定制的治疗计划进行了验证实验。对于这些计划，分别验证了 110.0 cm-117.5 cm 范围内的驻留位置和 2 s-16 s 范围内的驻留时间，并且证明了源强度与 S 之间的线性关系，源强度范围在 28 348 U（cGy cm h）到 41 906 U 之间。对于各种 5 mm 到 50 mm 的距离，计算了放射性源的线速度，即驻留位置之间距离的平均速度。结果表明，与计划值相比，测量的驻留位置和驻留时间的平均偏差分别为 0.1 mm（范围为 0 到 0.2 mm）和 32.5 ms（范围为 0 到 60.0 ms），系统响应与 S 高度线性相关（R = 0.998）。此外，测量的线速度与先前报道的值相当。得益于紧凑的硬件设计和图像处理算法，该系统为 HDR QA 提供了一种实用、可靠和全面的解决方案。
