Kanani Abolfazl, Owrangi Amir, Yazdi Mehran, Fatemi-Ardekani Ali, Mosleh-Shirazi Mohammad Amin
Ionizing and Non-Ionizing Radiation Protection Research Center (INIRPRC), School of Paramedical Sciences, Shiraz University of Medical Sciences, Shiraz, Iran.
Department of Radiation Oncology, UT Southwestern Medical Center, Dallas, TX, USA.
J Contemp Brachytherapy. 2023 Feb;15(1):57-68. doi: 10.5114/jcb.2023.125014. Epub 2023 Feb 10.
Suitable commissioning and quality control (QC) tests for high-dose-rate brachytherapy (HDR-BT) is necessary to ensure dosimetric and geometric accuracy of the treatment. This study aimed to present the methodology of developing a novel multi-purpose QC phantom (AQuA-BT) and examples of its' application in 3D image-based (particularly magnetic resonance imaging [MRI]-based) planning for cervix BT.
Design criteria led to a phantom with sufficient size waterproof box for dosimetry and capability for inserting other components inside the phantom for: (A) Validating dose calculation algorithms in treatment planning systems (TPSs) using a small-volume ionization chamber; (B) Testing volume calculation accuracy in TPSs for bladder, rectum, and sigmoid organs at risk (OARs) constructed by 3D printing; (C) Quantification of MRI distortions using 17 semi-elliptical plates with 4,317 control points to mimic a realistic female's pelvis size; and (D) Quantification of image distortions and artifacts induced by MRI-compatible applicators using a specific radial fiducial marker. The utility of the phantom was tested in various QC procedures.
The phantom was successfully implemented for examples of intended QC procedures. The maximum deviation between the absorbed doses to water assessed with our phantom and those calculated by SagiPlan TPS was 1.7%. The mean discrepancy in volumes of TPS-calculated OARs was 1.1%. The differences between known distances within the phantom on MR imaging were within 0.7 mm compared with computed tomography.
This phantom is a promising useful tool for dosimetric and geometric quality assurance (QA) in MRI-based cervix BT.
对于高剂量率近距离放射治疗（HDR - BT），合适的调试和质量控制（QC）测试对于确保治疗的剂量学和几何精度是必要的。本研究旨在介绍一种新型多功能QC体模（AQuA - BT）的开发方法及其在基于三维图像（特别是基于磁共振成像[MRI]）的子宫颈BT治疗计划中的应用实例。
设计标准导致了一个具有足够尺寸的防水盒体模用于剂量学研究，并且能够在体模内部插入其他组件以用于：（A）使用小体积电离室在治疗计划系统（TPS）中验证剂量计算算法；（B）测试TPS中通过3D打印构建的膀胱、直肠和乙状结肠等危及器官（OARs）的体积计算准确性；（C）使用带有4317个控制点的17个半椭圆形板来模拟实际女性骨盆大小，以量化MRI畸变；以及（D）使用特定的径向基准标记来量化由MRI兼容施源器引起的图像畸变和伪影。在各种QC程序中测试了该体模的实用性。
该体模成功应用于预期的QC程序示例。用我们的体模评估的水吸收剂量与SagiPlan TPS计算的剂量之间的最大偏差为1.7%。TPS计算的OARs体积的平均差异为1.1%。与计算机断层扫描相比，体模在MR成像上已知距离之间的差异在0.7毫米以内。
该体模是基于MRI的子宫颈BT剂量学和几何质量保证（QA）的一种很有前景的有用工具。
