OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden - Rossendorf, Dresden, Germany; Helmholtz-Zentrum Dresden - Rossendorf, Institute of Radiooncology - OncoRay, Dresden, Germany.
OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden - Rossendorf, Dresden, Germany; Helmholtz-Zentrum Dresden - Rossendorf, Institute of Radiooncology - OncoRay, Dresden, Germany.
Radiother Oncol. 2021 Oct;163:7-13. doi: 10.1016/j.radonc.2021.07.019. Epub 2021 Jul 27.
Experimental assessment of inter-centre variation and absolute accuracy of stopping-power-ratio (SPR) prediction within 17 particle therapy centres of the European Particle Therapy Network.
A head and body phantom with seventeen tissue-equivalent materials were scanned consecutively at the participating centres using their individual clinical CT scan protocol and translated into SPR with their in-house CT-number-to-SPR conversion. Inter-centre variation and absolute accuracy in SPR prediction were quantified for three tissue groups: lung, soft tissues and bones. The integral effect on range prediction for typical clinical beams traversing different tissues was determined for representative beam paths for the treatment of primary brain tumours as well as lung and prostate cancer.
An inter-centre variation in SPR prediction (2σ) of 8.7%, 6.3% and 1.5% relative to water was determined for bone, lung and soft-tissue surrogates in the head setup, respectively. Slightly smaller variations were observed in the body phantom (6.2%, 3.1%, 1.3%). This translated into inter-centre variation of integral range prediction (2σ) of 2.9%, 2.6% and 1.3% for typical beam paths of prostate-, lung- and primary brain-tumour treatments, respectively. The absolute error in range exceeded 2% in every fourth participating centre. The consideration of beam hardening and the execution of an independent HLUT validation had a positive effect, on average.
The large inter-centre variations in SPR and range prediction justify the currently clinically used margins accounting for range uncertainty, which are of the same magnitude as the inter-centre variation. This study underlines the necessity of higher standardisation in CT-number-to-SPR conversion.
在欧洲粒子治疗网络的 17 个粒子治疗中心内，对阻止比（SPR）预测的中心间差异和绝对准确性进行实验评估。
使用参与中心各自的临床 CT 扫描方案，对头部和身体体模进行连续扫描，并将其转换为 SPR，使用各自的 CT 值到 SPR 的转换。针对三种组织类型（肺、软组织和骨骼），对 SPR 预测的中心间差异和绝对准确性进行了量化。为治疗原发性脑肿瘤、肺癌和前列腺癌的典型临床射束确定了穿过不同组织的典型射束路径的范围预测的积分效应。
在头部设置中，分别确定了骨骼、肺和软组织替代物的 SPR 预测（2σ）的中心间变化为 8.7%、6.3%和 1.5%，相对于水。在身体体模中观察到的变化稍小（6.2%、3.1%、1.3%）。这转化为典型前列腺癌、肺癌和原发性脑肿瘤治疗射束路径的积分范围预测（2σ）的中心间变化分别为 2.9%、2.6%和 1.3%。在每四个参与中心中，有一个中心的范围内绝对误差超过 2%。考虑到束硬化并执行独立的 HLUT 验证，平均而言具有积极的效果。
SPR 和范围预测的大中心间变化证明了当前临床上使用的考虑范围不确定性的边缘是合理的，其与中心间变化具有相同的量级。这项研究强调了 CT 值到 SPR 转换更高标准化的必要性。
