Department of Biomedical Physics in Radiation Oncology, Deutsches Krebsforschungszentrum (DKFZ), Heidelberg, Germany.
Department of Physics and Astronomy, Heidelberg University, Heidelberg, Germany.
Phys Med Biol. 2021 Nov 29;66(23). doi: 10.1088/1361-6560/ac33ec.
This work provides a quantitative assessment of helium ion CT (HeCT) for particle therapy treatment planning. For the first time, HeCT based range prediction accuracy in a heterogeneous tissue phantom is presented and compared to single-energy x-ray CT (SECT), dual-energy x-ray CT (DECT) and proton CT (pCT). HeCT and pCT scans were acquired using the US pCT collaboration prototype particle CT scanner at the Heidelberg Ion-Beam Therapy Center. SECT and DECT scans were done with a Siemens Somatom Definition Flash and converted to RSP. A Catphan CTP404 module was used to study the RSP accuracy of HeCT. A custom phantom of 20 cm diameter containing several tissue equivalent plastic cubes was used to assess the spatial resolution of HeCT and compare it to DECT. A clinically realistic heterogeneous tissue phantom was constructed using cranial slices from a pig head placed inside a cylindrical phantom (ø150 mm). A proton beam (84.67 mm range) depth-dose measurement was acquired using a stack of GafchromicTM EBT-XD films in a central dosimetry insert in the phantom. CT scans of the phantom were acquired with each modality, and proton depth-dose estimates were simulated based on the reconstructions. The RSP accuracy of HeCT for the plastic phantom was found to be 0.3 ± 0.1%. The spatial resolution for HeCT of the cube phantom was 5.9 ± 0.4 lp cmfor central, and 7.6 ± 0.8 lp cmfor peripheral cubes, comparable to DECT spatial resolution (7.7 ± 0.3 lp cmand 7.4 ± 0.2 lp cm, respectively). For the pig head, HeCT, SECT, DECT and pCT predicted range accuracy was 0.25%, -1.40%, -0.45% and 0.39%, respectively. In this study, HeCT acquired with a prototype system showed potential for particle therapy treatment planning, offering RSP accuracy, spatial resolution, and range prediction accuracy comparable to that achieved with a commercial DECT scanner. Still, technical improvements of HeCT are needed to enable clinical implementation.
这项工作对氦离子 CT（HeCT）在粒子治疗计划中的应用进行了定量评估。本文首次提出并比较了基于 HeCT 的不均匀组织体模中的射程预测精度，比较对象包括单能量 X 射线 CT（SECT）、双能 X 射线 CT（DECT）和质子 CT（pCT）。HeCT 和 pCT 扫描是在海德堡离子束治疗中心使用美国 pCT 合作项目的原型粒子 CT 扫描仪进行的。SECT 和 DECT 扫描是使用西门子 Somatom Definition Flash 完成的，并转换为 RSP。Catphan CTP404 模块用于研究 HeCT 的 RSP 精度。使用直径为 20 厘米的包含几个组织等效塑料方块的定制体模来评估 HeCT 的空间分辨率，并将其与 DECT 进行比较。使用猪头部的颅切片放置在圆柱形体模（ø150 毫米）内部构建了一个临床逼真的不均匀组织体模。使用圆柱形体模中央剂量学插件中的一组 GafchromicTM EBT-XD 胶片获得质子束（84.67 毫米射程）深度剂量测量值。使用每种模态对体模进行 CT 扫描，并根据重建结果模拟质子深度剂量估计值。发现 HeCT 对塑料体模的 RSP 精度为 0.3±0.1%。HeCT 对立方体形模的空间分辨率为中心 5.9±0.4lp cm，外围 7.6±0.8lp cm，与 DECT 空间分辨率（分别为 7.7±0.3lp cm和 7.4±0.2lp cm）相当。对于猪头部，HeCT、SECT、DECT 和 pCT 预测的射程精度分别为 0.25%、-1.40%、-0.45%和 0.39%。在这项研究中，使用原型系统获取的 HeCT 显示出在粒子治疗计划中的应用潜力，其 RSP 精度、空间分辨率和射程预测精度与商用 DECT 扫描仪相当。然而，仍需要对 HeCT 进行技术改进，以实现临床应用。
