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, Dresden, Germany.
German Cancer Research Center, Heidelberg, Germany; National Center for Radiation Research in Oncology, Heidelberg Institute for Radiation Oncology, Heidelberg, Germany.
Int J Radiat Oncol Biol Phys. 2017 Feb 1;97(2):427-434. doi: 10.1016/j.ijrobp.2016.10.022. Epub 2016 Oct 21.
To determine whether a standardized clinical application of dual-energy computed tomography (DECT) for proton treatment planning based on pseudomonoenergetic CT scans (MonoCTs) is feasible and increases the precision of proton therapy in comparison with single-energy CT (SECT).
To define an optimized DECT protocol, CT scan settings were analyzed experimentally concerning beam hardening, image quality, and influence on the heuristic conversion of CT numbers into stopping-power ratios (SPRs) and were compared with SECT scans with identical CT dose. Differences in range prediction and dose distribution between SECT and MonoCT were quantified for phantoms and a patient.
Dose distributions planned on SECT and MonoCT datasets revealed mean range deviations of 0.3 mm, γ passing rates (1%, 1 mm) greater than 99.9%, and no clinically relevant changes in dose-volume histograms. However, image noise and CT-related uncertainties could be reduced by MonoCT compared with SECT, which resulted in a slightly decreased dependence of SPR prediction on beam hardening. Consequently, DECT was clinically implemented at the University Proton Therapy Dresden in 2015. Until October 2016, 150 patients were treated based on MonoCTs, and more than 950 DECT scans of 351 patients were acquired during radiation therapy.
A standardized clinical use of MonoCT for treatment planning is feasible, leads to improved image quality and SPR prediction, extends diagnostic variety, and enables a stepwise clinical implementation of DECT toward a physics-based, patient-specific, nonheuristic SPR determination. Further reductions of CT-related uncertainties, as expected from such SPR approaches, can be evaluated on the resulting DECT patient database.
确定基于伪单能量 CT 扫描（MonoCT）的质子治疗计划的双能 CT（DECT）是否可以标准化临床应用，与单能量 CT（SECT）相比是否能提高质子治疗的精度。
为了定义优化的 DECT 方案，我们对 CT 扫描参数进行了实验分析，重点是束硬化、图像质量以及对 CT 数转换为阻止比（SPR）的启发式转换的影响，并与具有相同 CT 剂量的 SECT 扫描进行了比较。对体模和患者分别量化了 SECT 和 MonoCT 之间的射程预测和剂量分布差异。
在 SECT 和 MonoCT 数据集上计划的剂量分布显示平均射程偏差为 0.3 毫米，γ通过率（1%，1 毫米）大于 99.9%，剂量体积直方图无明显变化。然而，与 SECT 相比，MonoCT 可以降低图像噪声和 CT 相关的不确定性，这导致 SPR 预测对束硬化的依赖性略有降低。因此，2015 年德累斯顿质子治疗大学在临床上实施了 DECT。截至 2016 年 10 月，基于 MonoCT 治疗了 150 名患者，在放射治疗期间共获取了 351 名患者的超过 950 次 DECT 扫描。
MonoCT 用于治疗计划的标准化临床应用是可行的，可提高图像质量和 SPR 预测，扩展诊断范围，并为基于物理、患者特异性、非启发式 SPR 确定的 DECT 的逐步临床实施奠定基础。预计此类 SPR 方法将进一步降低 CT 相关的不确定性，这可以在产生的 DECT 患者数据库中进行评估。
