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Pre-treatment and real-time image guidance for a fixed-beam radiotherapy system
Physics in Medicine & Biology ( IF 3.5 ) Pub Date : 2021-03-04 , DOI: 10.1088/1361-6560/abdc12
Paul Z Y Liu 1 , Mark Gardner 1 , Soo Min Heng 2 , Chun-Chen Shieh 1 , Doan Trang Nguyen 1, 3 , Emily Debrot 1 , Ricky O'Brien 1 , Simon Downes 2 , Michael Jackson 2 , Paul J Keall 1
Affiliation  

Purpose. A radiotherapy system with a fixed treatment beam and a rotating patient positioning system could be smaller, more robust and more cost effective compared to conventional rotating gantry systems. However, patient rotation could cause anatomical deformation and compromise treatment delivery. In this work, we demonstrate an image-guided treatment workflow with a fixed beam prototype system that accounts for deformation during rotation to maintain dosimetric accuracy. Methods. The prototype system consists of an Elekta Synergy linac with the therapy beam orientated downward and a custom-built patient rotation system (PRS). A phantom that deforms with rotation was constructed and rotated within the PRS to quantify the performance of two image guidance techniques: motion compensated cone-beam CT (CBCT) for pre-treatment volumetric imaging and kilovoltage infraction monitoring (KIM) for real-time image guidance. The phantom was irradiated with a 3D conformal beam to evaluate the dosimetric accuracy of the workflow. Results. The motion compensated CBCT was used to verify pre-treatment position and the average calculated position was within −0.31.1 mm of the phantom’s ground truth position at 0. KIM tracked the position of the target in real-time as the phantom was rotated and the average calculated position was within −0.20.8 mm of the phantom’s ground truth position. A 3D conformal treatment delivered on the prototype system with image guidance had a 3%/2 mm gamma pass rate of 96.3% compared to 98.6% delivered using a conventional rotating gantry linac. Conclusions. In this work, we have shown that image guidance can be used with fixed-beam treatment systems to measure and account for changes in target position in order to maintain dosimetric coverage during horizontal rotation. This treatment modality could provide a viable treatment option when there insufficient space for a conventional linear accelerator or where the cost is prohibitive.



中文翻译:

固定束放射治疗系统的预处理和实时图像引导

目的。与传统的旋转机架系统相比,具有固定治疗束和旋转患者定位系统的放射治疗系统可以更小、更坚固且更具成本效益。然而,患者轮换可能会导致解剖变形并影响治疗实施。在这项工作中,我们展示了一个带有固定光束原型系统的图像引导治疗工作流程,该系统考虑了旋转过程中的变形以保持剂量测量精度。方法. 原型系统由一个治疗光束向下定向的 Elekta Synergy 直线加速器和一个定制的患者旋转系统 (PRS) 组成。在 PRS 内构建和旋转变形的模型以量化两种图像引导技术的性能:用于治疗前体积成像的运动补偿锥形束 CT (CBCT) 和用于实时图像的千伏电压侵犯监测 (KIM)指导。用 3D 保形光束照射体模,以评估工作流程的剂量测量精度。结果. 运动补偿 CBCT 用于验证预处理位置,平均计算位置在 0 时体模真实位置的 -0.31.1 mm 范围内。KIM 在体模旋转时实时跟踪目标的位置,并计算出的平均位置在体模真实位置的 -0.20.8 mm 范围内。在具有图像引导的原型系统上交付的 3D 保形治疗具有 96.3% 的 3%/2 mm 伽马通过率,而使用传统旋转龙门直线加速器交付的伽马通过率为 98.6%。结论. 在这项工作中,我们已经表明,图像引导可以与固定光束治疗系统一起使用,以测量和解释目标位置的变化,以便在水平旋转期间保持剂量覆盖。当传统的直线加速器空间不足或成本过高时,这种治疗方式可以提供一种可行的治疗选择。

更新日期:2021-03-04
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