Nelson Nicholas, Oare Courtney, Nelson Geoff, Martin Thomas, Huang Jessica, Zhao Hui
Department of Radiation Oncology, University of Utah, Salt Lake City, Utah, USA.
J Appl Clin Med Phys. 2025 Sep;26(9):e70245. doi: 10.1002/acm2.70245.
The development of on-board cone-beam computed tomography (CBCT) has led to improved target localization and evaluation of patient anatomical change throughout the course of radiation therapy. HyperSight, a newly developed on-board CBCT platform by Varian, has been shown to improve image quality and HU fidelity relative to conventional CBCT. The purpose of this study is to benchmark the dose calculation accuracy of Varian's HyperSight cone-beam computed tomography (CBCT) on the Halcyon platform relative to fan-beam CT-based dose calculations and to perform end-to-end testing of HyperSight CBCT-only based treatment planning.
A HU to mass density curve was measured for the HyperSight CBCT system and implemented into the Eclipse treatment planning system. Following this, computational dosimetric analysis was performed between dose distributions calculated on CT simulation (CT) and HyperSight CBCT images on two anthropomorphic phantoms for pelvic and head and neck treatment sites. Additionally, an end-to-end test was carried out for a head and neck intensity modulated radiation therapy (IMRT) plan.
The HU to mass density curves acquired on CT and HyperSight CBCT were similar (< 30 HU) for near-water equivalent materials, but deviated for high-density materials, with a maximum difference of 150 HU. For dose calculations, excellent agreement between dose calculations performed on CT and HyperSight CBCT phantom images was observed, where three-dimensional gamma pass rates between the two dose distributions were observed to be 90% at 1%/1 mm (5% threshold). For the end-to-end test, absolute doses were verified to within 1% of ionization chamber measurements, while Delta4+ and portal dosimetry measurements yielded passing results (gamma pass rate 90%) down to 2%/2 mm criterion.
In this study, the accuracy of dose calculations performed on HyperSight CBCT was found to be within 1% of CT calculations for pelvic and head and neck treatment sites. End-to-end results using the RANDO anthropomorphic phantom indicate that HyperSight CBCT images are suitable for radiation treatment planning.
机载锥形束计算机断层扫描（CBCT）的发展使得在放射治疗过程中靶区定位得到改善，并且能够评估患者的解剖结构变化。Varian公司新开发的机载CBCT平台HyperSight，已被证明相对于传统CBCT可提高图像质量和HU保真度。本研究的目的是将Varian公司Halcyon平台上的HyperSight锥形束计算机断层扫描（CBCT）的剂量计算准确性与基于扇形束CT的剂量计算进行对比，并对仅基于HyperSight CBCT的治疗计划进行端到端测试。
测量了HyperSight CBCT系统的HU与质量密度曲线，并将其应用于Eclipse治疗计划系统。在此之后，对盆腔和头颈部治疗部位的两个人体模型，在CT模拟（CT）图像和HyperSight CBCT图像上计算的剂量分布之间进行了剂量学计算分析。此外，对头颈部调强放射治疗（IMRT）计划进行了端到端测试。
对于近水等效材料，在CT和HyperSight CBCT上获取的HU与质量密度曲线相似（<30 HU），但对于高密度材料则存在偏差，最大差值为150 HU。对于剂量计算，观察到在CT和HyperSight CBCT体模图像上进行的剂量计算之间具有良好的一致性，在1%/1 mm（5%阈值）时，两种剂量分布之间的三维伽马通过率为90%。对于端到端测试，绝对剂量经验证与电离室测量值相差在1%以内，而Delta4+和门静脉剂量测量在2%/2 mm标准下得出合格结果（伽马通过率>90%）。
在本研究中，发现对于盆腔和头颈部治疗部位，在HyperSight CBCT上进行的剂量计算准确性与CT计算相差在1%以内。使用RANDO人体模型的端到端结果表明，HyperSight CBCT图像适用于放射治疗计划。
