Bratova Iva, Paluska Petr, Grepl Jakub, Sykorova Petra, Jansa Jan, Hodek Miroslav, Sirak Igor, Vosmik Milan, Petera Jiri
Department of Oncology and Radiotherapy, University Hospital Hradec Kralove, Czech Republic.
Rep Pract Oncol Radiother. 2019 Mar-Apr;24(2):245-250. doi: 10.1016/j.rpor.2019.02.001. Epub 2019 Feb 28.
To evaluate calculation of treatment plans based on synthetic-CT (sCT) images generated from MRI.
Because of better soft tissue contrast, MR images are used in addition to CT images for radiotherapy planning. However, registration of CT and MR images or repositioning between scanning sessions introduce systematic errors, hence suggestions for MRI-only therapy. The lack of information on electron density necessary for dose calculation leads to sCT (synthetic CT) generation. This work presents a comparison of dose distribution calculated on standard CT and sCT.
10 prostate patients were included in this study. CT and MR images were collected for each patient and then water equivalent (WE) and MRCAT images were generated. The radiation plans were optimized on CT and then recalculated on MRCAT and WE data. 2D gamma analysis was also performed.
The mean differences in the majority of investigated DVH points were in order of 1% up to 10%, including both MRCAT and WE dose distributions. Mean gamma pass for acceptance criteria 1%/1 mm were greater than 82.5%. Prescribed doses for target volumes and acceptable doses for organs at risk were met in almost all cases.
The dose calculation accuracy on MRCAT was not significantly compromised in the majority of clinical relevant DVH points. The introduction of MRCAT into practise would eliminate systematic errors, increase patients' comfort and reduce treatment expenses. Institutions interested in MRCAT commissioning must, however, consider changes to established workflow.
评估基于磁共振成像（MRI）生成的合成CT（sCT）图像的治疗计划计算。
由于软组织对比度更好，在放射治疗计划中，除了CT图像外还使用MRI图像。然而，CT和MRI图像的配准或扫描期间的重新定位会引入系统误差，因此有人建议采用仅基于MRI的治疗方法。由于缺乏剂量计算所需的电子密度信息，导致了合成CT（sCT）的产生。本文对在标准CT和sCT上计算的剂量分布进行了比较。
本研究纳入了10例前列腺癌患者。为每位患者收集CT和MRI图像，然后生成水等效（WE）和MRCAT图像。在CT上优化放射治疗计划，然后在MRCAT和WE数据上重新计算。还进行了二维伽马分析。
在大多数研究的剂量体积直方图（DVH）点上，平均差异在1%到10%之间，包括MRCAT和WE剂量分布。对于1%/1毫米的验收标准，平均伽马通过率大于82.5%。几乎在所有情况下都达到了靶区的处方剂量和危及器官的可接受剂量。
在大多数临床相关的DVH点上，MRCAT的剂量计算准确性没有受到显著影响。将MRCAT引入实践将消除系统误差，提高患者舒适度并降低治疗费用。然而，对MRCAT调试感兴趣的机构必须考虑对既定工作流程的改变。
