Technical Note: End‐to‐end verification of an MR‐Linac using a dynamic motion phantom

作者：Xuechun Liu, Chengqiang Li, Jian Zhu, Guanzhong Gong, Hongqiang Sun, Xu Li, Mengdi Sun, Zicheng Zhang, Baosheng Li, Yong Yin, Zhenjiang Li · 发表于：Medical Physics · 年份：2021 · DOI：10.1002/mp.15057 · 被引用次数：14 · 研究领域：Advanced Radiotherapy Techniques、Radiation Therapy and Dosimetry、Hepatocellular Carcinoma Treatment and Prognosis

PURPOSE: MR-Linac integrates an MRI scanner and a linear accelerator to provide adaptive radiation treatment. Superior tissue contrast and real-time imaging can give the clinicians confidence to reduce the margins of the planning target volume (PTV). The purpose of this study was to verify the dosimetric accuracy of an MR-Linac system in treating a moving target and assess the error with different motion patterns and adaptation methods. METHODS: We performed an end-to-end test for Elekta Unity (Elekta) using the 4D Dynamic Thorax Phantom (CIRS MRgRT 008Z), comparing the measured and planned dose. The moving phantom had four measurement locations in the tumor, liver, kidney, and spinal cord regions with a PTW30013 ion chamber. For seven different motion patterns, we first acquired simulation CT using a slow-scanning protocol, based on which we generated reference plans. The treatment technique was the standard intensity-modulated radiation therapy (IMRT). We tested both adaptation workflows: the Adapt-to-Position (ATP) and the Adapt-to-Shape (ATS). The three-dimensional (3D) distribution was measured using a diode array phantom (Sun Nuclear Inc.) to check the dose distribution accuracy as part of the routine QA process. We also performed end-to-end tests on a conventional Linac. Finally, we used SPSS Statistics 22.0 (Inc., Chicago, IL, USA) for data analysis. RESULTS: All pretreatment reference plans and delivered plans had excellent QA results with a better than 95% passing r...