Department of Radiotherapy, University Medical Center, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands.
Phys Med Biol. 2013 May 7;58(9):2989-3000. doi: 10.1088/0031-9155/58/9/2989. Epub 2013 Apr 15.
When delivering conventional intensity modulated radiotherapy (IMRT), discrepancies between the pre-treatment CT/MRI/PET based patient geometry and the daily patient geometry are minimized by performing couch translations and/or small rotations. However, full compensation of, in particular, rotations is usually not possible. In this paper, we introduce an online 'virtual couch shift (VCS)': we translate and/or rotate the pre-treatment dose distribution to compensate for the changes in patient anatomy and generate a new plan which delivers the transformed dose distribution automatically. We show for a phantom and a cervical cancer patient case that VCS accounts for both translations and large rotations equally well in terms of DVH results and 2%/2 mm γ analyses and when the various aspects of the clinical workflow can be implemented successfully, VCS can potentially outperform physical couch translations and/or rotations. This work is performed in the context of our hybrid 1.5 T MRI linear accelerator, which can provide translations and rotations but also deformations of the anatomy. The VCS is the first step toward compensating all of these anatomical changes by online re-optimization of the IMRT dose distribution.
在提供常规强度调制放疗 (IMRT) 时，通过执行治疗床平移和/或小角度旋转，可以最大程度地减少基于治疗前 CT/MRI/PET 的患者几何形状与每日患者几何形状之间的差异。然而，通常无法完全补偿特别是旋转。在本文中，我们引入了一种在线“虚拟治疗床平移 (VCS)”:我们平移和/或旋转治疗前的剂量分布，以补偿患者解剖结构的变化，并生成一个新的计划，自动输送变换后的剂量分布。我们通过对一个体模和一个宫颈癌患者病例的研究表明，就剂量体积直方图 (DVH) 结果和 2%/2 毫米γ分析而言，VCS 在平移和大角度旋转方面的表现同样出色，并且当临床工作流程的各个方面都能够成功实施时，VCS 可能优于物理治疗床平移和/或旋转。这项工作是在我们的混合 1.5 T MRI 直线加速器的背景下进行的，该加速器可以提供平移和旋转，还可以对解剖结构进行变形。VCS 是通过在线重新优化 IMRT 剂量分布来补偿所有这些解剖变化的第一步。
