Bell Katharina, Heitfeld Marina, Licht Norbert, Rübe Christian, Dzierma Yvonne
Department of Radiotherapy and Radiation Oncology, Saarland University Medical Centre, Kirrberger Str. Geb. 6.5, D-66421, Homburg/Saar, Germany.
Radiat Oncol. 2017 Jan 10;12(1):7. doi: 10.1186/s13014-016-0757-9.
Modern radiotherapy offers various possibilities for image guided verification of patient positioning. Different clinically relevant IGRT (image guided radiotherapy) scenarios were considered with regard to their influence on dosimetric plan quality and normal tissue complication probability (NTCP).
This study is based on treatment plans of 50 prostate patients. We evaluate the clinically performed IGRT and simulate the influence of different daily IGRT scenarios on plan quality. Imaging doses of planar and cone-beam-CT (CBCT) images for three different energies (6 MV, 1 MV and 121 kV) were added to the treatment plans. The plan quality of the different scenarios was assessed by a visual inspection of the dose distribution and dose-volume-histogram (DVH) and a statistical analysis of DVH criteria. In addition, an assessment of the normal tissue complication probability was performed.
Daily 1MV-CBCTs result in undesirable high dose regions in the target volume. The DVH shows that the scenarios with actual imaging performed, daily kV-CBCT and daily 6MV imaging (1x CBCT, 4x planar images per week) do not differ exceedingly from the original plan; especially imaging with daily kV-CBCT has little influence to the sparing of organs at risk. In contrast, daily 1MV- CBCT entails an additional dose of up to two fraction doses. Due to the additional dose amount some DVH constraints for plan acceptability could no longer be satisfied, especially for the daily 1MV-CBCT scenario. This scenario also shows increased NTCP for the rectum.
Daily kV-CBCT has negligible influence on plan quality and is commendable for the clinical routine. If no kV-modality is available, a daily IGRT scenario with one CBCT per week and planar axial images on the other days should be preferred over daily MV-CBCT.
现代放射治疗为患者体位的图像引导验证提供了多种可能性。考虑了不同临床相关的图像引导放射治疗（IGRT）方案对剂量计划质量和正常组织并发症概率（NTCP）的影响。
本研究基于50例前列腺癌患者的治疗计划。我们评估了临床实施的IGRT，并模拟了不同每日IGRT方案对计划质量的影响。将三种不同能量（6MV、1MV和121kV）的平面和锥形束CT（CBCT）图像的成像剂量添加到治疗计划中。通过对剂量分布和剂量体积直方图（DVH）的目视检查以及DVH标准的统计分析来评估不同方案的计划质量。此外，还对正常组织并发症概率进行了评估。
每日1MV-CBCT会在靶区内产生不理想的高剂量区域。DVH显示，实际进行成像的方案、每日kV-CBCT和每日6MV成像（每周1次CBCT，4次平面图像）与原始计划的差异不大；特别是每日kV-CBCT成像对危及器官的 sparing影响很小。相比之下，每日1MV-CBCT会带来高达两个分次剂量的额外剂量。由于额外的剂量，一些计划可接受性的DVH限制不再能够满足，特别是对于每日1MV-CBCT方案。该方案还显示直肠的NTCP增加。
每日kV-CBCT对计划质量的影响可忽略不计，值得在临床常规中采用。如果没有kV模式，每周一次CBCT和其他日子的平面轴向图像的每日IGRT方案应优于每日MV-CBCT。
