Kaur Guneet, Lehmann Joerg, Greer Peter, Simpson John
Department of Radiation Oncology, Calvary Mater Newcastle Hospital, Newcastle, NSW, Australia.
School of Mathematical and Physical Sciences, Faculty of Science and IT, University of Newcastle, Newcastle, NSW, Australia.
Australas Phys Eng Sci Med. 2019 Jun;42(2):585-598. doi: 10.1007/s13246-019-00760-7. Epub 2019 May 13.
Intrafraction motion review (IMR), a real-time 2D, motion management feature of the Varian Truebeam™ incorporates triggered imaging, automatic fiducial marker detection and automatic beam hold. With the increasing adoption of high dose per fraction stereotactic body radiotherapy (SBRT) this system provides a potential means to ensure treatment accuracy. The goal of this study was therefore to investigate and quantify key performance characteristics of IMR for prostate treatment guidance. Phantom experiments were performed with a custom Computerized Imaging Reference Systems, Inc (CIRS) pelvis phantom with implanted gold seeds and the Hexamotion™ 5D motion platform. The system accuracy was assessed statically and under typical prostate motion trajectories. The IMR functionality and marker detectability was tested under different anatomical conditions and with different imaging acquisition modes. Imaging dose for triggered imaging modes was determined using an ionisation chamber based on IPEMB dose calibration protocol for kV energies. For zero displacement, the IMR demonstrated submillimeter agreement with the known position. Similarly, dynamic motion differences between the IMR reported position and 2D trajectory displacement were within 1 mm. Static displacement in the anterior direction was reported by IMR as sinusoidal motion on the x-axis (kV angle). The 2D nature of IMR limits the ability to detect motion out of the plane of the kV image detector. Using typical clinical imaging settings, imaging dose determined at the patient surface was 2.58 mGy/frame and the corresponding IMR displayed dose was 2.63 mGy/frame. The methodology used was able to quantify the accuracy of the IMR system. The IMR was able to accurately and consistently report fiducial positions within the limitations inherent of a 2D system. IMR is fully integrated with the Truebeam system with an easy to use and efficient workflow and is clinically beneficial especially within the context of SBRT.
分次内运动回顾（IMR）是瓦里安Truebeam™的一项实时二维运动管理功能，它结合了触发成像、自动基准标记检测和自动束流保持功能。随着高剂量分次立体定向体部放疗（SBRT）的日益普及，该系统提供了一种确保治疗准确性的潜在手段。因此，本研究的目的是调查和量化IMR在前列腺治疗引导方面的关键性能特征。使用定制的计算机成像参考系统公司（CIRS）骨盆模型（植入金种子）和Hexamotion™ 5D运动平台进行了体模实验。在静态和典型前列腺运动轨迹下评估了系统精度。在不同解剖条件和不同成像采集模式下测试了IMR功能和标记可检测性。使用基于IPEMB kV能量剂量校准协议的电离室确定触发成像模式的成像剂量。对于零位移，IMR显示与已知位置的偏差在亚毫米范围内。同样，IMR报告位置与二维轨迹位移之间的动态运动差异在1毫米以内。IMR报告在前后方向上的静态位移为x轴（kV角度）上的正弦运动。IMR的二维特性限制了检测kV图像探测器平面外运动的能力。使用典型的临床成像设置，在患者体表确定的成像剂量为2.58 mGy/帧，相应的IMR显示剂量为2.63 mGy/帧。所采用的方法能够量化IMR系统的精度。IMR能够在二维系统固有的限制范围内准确且一致地报告基准位置。IMR与Truebeam系统完全集成，具有易于使用且高效的工作流程，在临床上尤其在SBRT背景下具有益处。
