Branchini M, Fiorino C, Dell'Oca I, Belli M L, Perna L, Di Muzio N, Calandrino R, Broggi S
Medical Physics Department, San Raffaele Scientific Institute, Milano, Italy.
Radiotherapy Department, San Raffaele Scientific Institute, Milano, Italy.
Phys Med. 2017 Jul;39:73-79. doi: 10.1016/j.ejmp.2017.05.070. Epub 2017 Jun 12.
The aim of this study was to test the feasibility and dosimetric accuracy of a method that employs planning CT-to-MVCT deformable image registration (DIR) for calculation of the daily dose for head and neck (HN) patients treated with Helical Tomotherapy (HT).
For each patient, the planning kVCT (CTplan) was deformably registered to the MVCT acquired at the 15th therapy session (MV15) with a B-Spline Free Form algorithm using Mattes mutual information (open-source software 3D Slicer), resulting in a deformed CT (CTdef). On the same day as MVCT15, a kVCT was acquired with the patient in the same treatment position (CT15). The original HT plans were recalculated both on CTdef and CT15, and the corresponding dose distributions were compared; local dose differences <2% of the prescribed dose (DD2%) and 2D/3D gamma-index values (2%-2mm) were assessed respectively with Mapcheck SNC Patient software (Sun Nuclear) and with 3D-Slicer.
On average, 87.9%±1.2% of voxels were found for DD2% (on average 27 slices available for each patient) and 94.6%±0.8% of points passed the 2D gamma analysis test while the 3D gamma test was satisfied in 94.8%±0.8% of body's voxels.
This study represents the first demonstration of the dosimetric accuracy of kVCT-to-MVCT DIR for dose of the day computations. The suggested method is sufficiently fast and reliable to be used for daily delivered dose evaluations in clinical strategies for adaptive Tomotherapy of HN cancer.
本研究旨在测试一种利用计划CT到MVCT的可变形图像配准（DIR）方法来计算接受螺旋断层放疗（HT）的头颈部（HN）患者每日剂量的可行性和剂量准确性。
对于每位患者，使用基于马泰斯互信息的B样条自由形式算法（开源软件3D Slicer）将计划千伏CT（CTplan）与在第15次治疗时获取的MVCT（MV15）进行可变形配准，得到变形CT（CTdef）。在获取MVCT15的同一天，让患者处于相同治疗体位获取千伏CT（CT15）。在CTdef和CT15上重新计算原始HT计划，并比较相应的剂量分布；分别使用Mapcheck SNC Patient软件（Sun Nuclear）和3D-Slicer评估局部剂量差异<规定剂量的2%（DD2%）以及2D/3D伽马指数值（2%-2mm）。
平均而言，DD2%的体素比例为87.9%±1.2%（每位患者平均有27层可用），94.6%±0.8%的点通过了2D伽马分析测试，而3D伽马测试在94.8%±0.8%的身体体素中得到满足。
本研究首次证明了kVCT到MVCT DIR用于当日剂量计算的剂量准确性。所建议的方法足够快速且可靠，可用于HN癌症自适应断层放疗临床策略中的每日交付剂量评估。
