Proton dose calculation based on converting dual-energy CT data to stopping power ratio (DEEDZ-SPR): a beam-hardening assessment
Proton dose calculation based on converting dual-energy CT data to stopping power ratio (DEEDZ-SPR): a beam-hardening assessment
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DOI：
10.1088/1361-6560/abae09
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发表时间：
2020-12-07
影响因子：
3.5
通讯作者：
Saito, Masatoshi
中科院分区：
文献类型：
--
作者：
Tanaka, Sodai;Noto, Yoshiyuki;Saito, Masatoshi
为了在粒子治疗计划中实现准确的停止功率比（SPR）预测，我们之前提出了通过电子密度和有效原子序数（Z(eff)）校准（DEEDZ-SPR）将双能（DE）计算机断层扫描（CT）数据转换为SPR的简单方法。本研究采用临床治疗计划系统（TPS； VQA, Hitachi Ltd, Tokyo）对质子束治疗进行DEEDZ-SPR转换方法的初步实施。因此，本文提出了一种用于拟人化幻体的质子治疗方案，以评估由DEEDZ-SPR转换获得的剂量计算对校准幻体尺寸变化的稳定性。使用双源CT （DSCT）扫描仪获取双能x线CT图像。使用相同的DSCT扫描仪进行单能量CT （SECT）扫描，以比较DEEDZ-SPR转换与基于SECT的SPR转换（SECT-SPR）。SPR校准所需的扫描仪特定参数从校准模体中的组织替代品的CT图像中获得。采用直径33 cm和直径18 cm的两个不同尺寸的校准模体进行SPR校准，研究了光束硬化对剂量学不确定度的影响。每组校正后的SPR数据应用于使用VQA TPS设计的质子治疗方案，并采用铅笔束算法对拟人幻影进行治疗。采用SECT-SPR转换的治疗方案在33 cm和18 cm幻影校准的剂量分布和剂量-体积直方图（DVHs）之间存在差异。相比之下，DEEDZ-SPR转换法得到的相应剂量分布与dvh几乎完全吻合。DEEDZ-SPR转换似乎是一种很有前途的方法，可以提供稳定的质子剂量计划，以对抗校准幻影和患者的尺寸变化。
To achieve an accurate stopping power ratio (SPR) prediction in particle therapy treatment planning, we previously proposed a simple conversion to the SPR from dual-energy (DE) computed tomography (CT) data via electron density and effective atomic number (Z(eff)) calibration (DEEDZ-SPR). This study was conducted to carry out an initial implementation of the DEEDZ-SPR conversion method with a clinical treatment planning system (TPS; VQA, Hitachi Ltd., Tokyo) for proton beam therapy. Consequently, this paper presents a proton therapy plan for an anthropomorphic phantom to evaluate the stability of the dose calculations obtained by the DEEDZ-SPR conversion against the variation of the calibration phantom size. Dual-energy x-ray CT images were acquired using a dual-source CT (DSCT) scanner. A single-energy CT (SECT) scan using the same DSCT scanner was also performed to compare the DEEDZ-SPR conversion with the SECT-based SPR (SECT-SPR) conversion. The scanner-specific parameters necessary for the SPR calibration were obtained from the CT images of tissue substitutes in a calibration phantom. Two calibration phantoms with different sizes (a 33 cm diameter phantom and an 18 cm diameter phantom) were used for the SPR calibrations to investigate the beam-hardening effect on dosimetric uncertainties. Each set of calibrated SPR data was applied to the proton therapy plan designed using the VQA TPS with a pencil beam algorithm for the anthropomorphic phantom. The treatment plans with the SECT-SPR conversion exhibited discrepancies between the dose distributions and the dose-volume histograms (DVHs) of the 33 cm and 18 cm phantom calibrations. In contrast, the corresponding dose distributions and the DVHs obtained using the DEEDZ-SPR conversion method coincided almost perfectly with each other. The DEEDZ-SPR conversion appears to be a promising method for providing proton dose plans that are stable against the size variations of the calibration phantom and the patient.