背景:放射治疗中需要当天高质量的3D解剖来适应治疗计划。对于基于X射线的在线CBCT工作流程,一种方法是创建合成CT或利用具有相应配准的扇形射束CT。如果使用可变形图像配准,前者可能会在剂量计算中引入不确定性。后者会给流程带来负担和复杂性,设施,还有病人.
目的:使用当天的CBCT,在治疗装置上获得的,对于直接剂量计算和计划适应可以克服这些限制。这项研究旨在评估在配备HyperSight的Halcyon直线加速器上获得的CBCT扫描中计算剂量的准确性。
方法:HyperSight的新CBCT重建算法包括对散射校正的改进,成像仪的HU校准,和光束形状适应。此外,HyperSight引入了一种新的X射线探测器。为了显示已实施改进的效果,2%/2毫米的伽马比较,2%/1毫米,在CBCT重建和模拟CT扫描计算的体模中的剂量分布之间进行1%/1mm,认为这是护理的标准。将所得的伽马通过率与使用Halcyon3.0重建和没有HyperSight技术的硬件获得的伽马通过率进行比较。用于对大脑进行剂量学评估的各种解剖体模,头部和颈部,肺,乳房,和前列腺病例已用于这项研究。
结果:总体结果表明,HyperSight优于Halcyon3.0版本。根据伽马分析,对于大多数病例,使用HyperSight计算的剂量比使用iCBCTHalcyon3.0计算的剂量更接近基于CT扫描的剂量.在所有计划和伽马标准上,Halcyon3.0取得了92.9%的平均通过率,而HyperSight达到98.1%。
结论:使用HyperSightCBCT图像进行直接剂量计算,例如,在(在线)计划适应中,对于调查的案件似乎是可行的。
BACKGROUND: High-quality 3D-anatomy of the day is needed for treatment plan adaptation in radiotherapy. For online x-ray-based CBCT workflows, one approach is to create a synthetic CT or to utilize a fan-beam CT with corresponding registrations. The former potentially introduces uncertainties in the dose calculation if deformable image registration is used. The latter can introduce burden and complexity to the process, the facility, and the patient.
OBJECTIVE: Using the CBCT of the day, acquired on the treatment device, for direct dose calculation and plan adaptation can overcome these limitations. This study aims to assess the accuracy of the calculated dose on the CBCT scans acquired on a Halcyon linear accelerator equipped with HyperSight.
METHODS: HyperSight\'s new CBCT reconstruction algorithm includes improvements in scatter correction, HU calibration of the imager, and beam shape adaptation. Furthermore, HyperSight introduced a new x-ray detector. To show the effect of the implemented improvements, gamma comparisons of 2%/2 mm, 2%/1 mm, and 1%/1 mm were made between the dose distribution in phantoms calculated on the CBCT reconstructions and the simulation CT scans, considering this the standard of care. The resulting gamma passing rates were compared to those obtained with the Halcyon 3.0 reconstruction and hardware without HyperSight\'s technologies. Various anatomical phantoms for dosimetric evaluations on brain, head and neck, lung, breast, and prostate cases have been used in this study.
RESULTS: The overall results demonstrated that HyperSight outperformed the Halcyon 3.0 version. Based on the gamma analysis, the calculated dose using HyperSight was closer to the CT scan-based doses than the calculated dose using iCBCT Halcyon 3.0 for most cases. Over all plans and gamma criteria, Halcyon 3.0 achieved an average passing rate of 92.9%, whereas HyperSight achieved 98.1%.
CONCLUSIONS: Using HyperSight CBCT images for direct dose calculation, for example, in (online) plan adaptation, seems feasible for the investigated cases.