Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia.
Department of Radiation Oncology, St George Cancer Care Centre, Kogarah, NSW, Australia.
Med Phys. 2024 Jul;51(7):4581-4590. doi: 10.1002/mp.17240. Epub 2024 Jun 5.
There currently exists no widespread high dose-rate (HDR) brachytherapy afterloader quality assurance (QA) tool for simultaneously assessing the afterloader's positional, temporal, transit velocity and air kerma strength accuracy.
The purpose of this study was to develop a precise and rigorous technique for performing daily QA of HDR brachytherapy afterloaders, incorporating QA of: dwell position accuracy, dwell time accuracy, transit velocity consistency and relative air kerma strength (AKS) of an Ir-192 source.
A Sharp ProGuide 240 mm catheter (Elekta Brachytherapy, Veenendaal, The Netherlands) was fixed 5 mm above a 256 channel epitaxial diode array 'dose magnifying glass' (DMG256) (Centre for Medical and Radiation Physics, University of Wollongong). Three dwell positions, each of 5.0 s dwell times, were spaced 13.0 mm apart along the array with the Flexitron HDR afterloader (Elekta Brachytherapy, Veenendaal, The Netherlands). The DMG256 was connected to a data acquisition system (DAQ) and a computer via USB2.0 link for live readout and post-processing. The outputted data files were analyzed using a Python script to provide positional and temporal localization of the Ir-192 source by tracking the centroid of the detected response. Measurements were repeated on a weekly basis, for a period of 5 weeks to determine the consistency of the measured parameters over an extended period.
Using the DMG256 for relative AKS measurements resulted in measured values within 0.6%-3.0% of the expected activity over a 7-week period. The sub-millisecond temporal accuracy of the device allowed for measurements of the transit velocity with an average of (10.88 ± 1.01) cm/s for 13 mm steps. The dwell position localization for 1, 2, 3, 5, and 10 mm steps had an accuracy between 0.1 and 0.3 mm (3σ), with a fixed temporal accuracy of 10 ms.
The DMG256 silicon strip detector allows for clinics to perform rigorous daily QA of HDR afterloader dwell position and dwell time accuracy with greater precision than the current standard methodology using closed circuit television and a stopwatch. Additionally, DMG256 unlocks the ability to perform measurements of transit velocity/time and relative AKS, which are not possible using current standard techniques.
目前尚无广泛使用的高剂量率（HDR）近距离治疗后装源质量保证（QA）工具，可同时评估后装源的位置、时间、传输速度和空气比释动能率准确性。
本研究旨在开发一种精确而严格的 HDR 近距离治疗后装源日常 QA 技术，对以下内容进行 QA：驻留位置精度、驻留时间精度、传输速度一致性和 Ir-192 源的相对空气比释动能率（AKS）。
将一根长 240mm 的 Sharp ProGuide 导管（荷兰 Elekta 近距离治疗）固定在一个 256 通道外延二极管阵列“剂量放大镜”（DMG256）上方 5mm 处（澳大利亚卧龙岗大学医学与辐射物理中心）。三个驻留位置，每个驻留时间为 5.0s，沿阵列间隔 13.0mm，使用 Flexitron HDR 后装源（荷兰 Elekta 近距离治疗）。DMG256 通过 USB2.0 链路连接到数据采集系统（DAQ）和计算机，用于实时读取和后期处理。使用 Python 脚本分析输出的数据文件，通过检测到的响应的质心来提供 Ir-192 源的位置和时间定位。每周重复测量，持续 5 周，以确定在较长时间内测量参数的一致性。
使用 DMG256 进行相对 AKS 测量，在 7 周内得到的测量值与预期活度在 0.6%到 3.0%之间。该设备的亚毫秒级时间精度允许以平均（10.88±1.01）cm/s 的速度测量 13mm 步长的传输速度。对于 1、2、3、5 和 10mm 步长的驻留位置定位，精度在 0.1 到 0.3mm（3σ）之间，固定时间精度为 10ms。
DMG256 硅条探测器使临床能够以前置电视和秒表等当前标准方法更精确地进行 HDR 后装源驻留位置和驻留时间精度的严格日常 QA。此外，DMG256 还可以实现传输速度/时间和相对 AKS 的测量，这是当前标准技术无法实现的。
