Anto Gipson Joe, Sekaran Sureka, Perumal Bojarajan, Ramar Natarajan, Vaitheeswaran R, Karthikeyan S K
Department of Medical Physics, Bharathiar University, Coimbatore, India.
Department of Physics, School of Advanced Sciences, Vellore Institute of Technology, Vellore, India.
Rep Pract Oncol Radiother. 2022 Mar 22;27(1):161-169. doi: 10.5603/RPOR.a2022.0015. eCollection 2022.
The objective of this study is to determine the impact of intensity modulated proton therapty (IMPT) optimization techniques on the proton dose comparison of commercially available magnetic resonance for calculating attenuation (MRCA T) images, a synthetic computed tomography CT (sCT) based on magnetic resonance imaging (MRI) scan against the CT images and find out the optimization technique which creates plans with the least dose differences against the regular CT image sets.
Regular CT data sets and sCT image sets were obtained for 10 prostate patients for the study. Six plans were created using six distinct IMPT optimization techniques including multi-field optimization (MFO), single field uniform dose (SFUD) optimization, and robust optimization (RO) in CT image sets. These plans were copied to MRCA T, sCT datasets and doses were computed. Doses from CT and MRCA T data sets were compared for each patient using 2D dose distribution display, dose volume histograms (DVH), homogeneity index (HI), conformation number (CN) and 3D gamma analysis. A two tailed t-test was conducted on HI and CN with 5% significance level with a null hypothesis for CT and sCT image sets.
Analysis of ten CT and sCT image sets with different IMPT optimization techniques shows that a few of the techniques show significant differences between plans for a few evaluation parameters. Isodose lines, DVH, HI, CN and t-test analysis shows that robust optimizations with 2% range error incorporated results in plans, when re-computed in sCT image sets results in the least dose differences against CT plans compared to other optimization techniques. The second best optimization technique with the least dose differences was robust optimization with 5% range error.
This study affirmatively demonstrates the impact of IMPT optimization techniques on synthetic CT image sets dose comparison against CT images and determines the robust optimization with 2% range error as the optimization technique which gives the least dose difference when compared to CT plans.
本研究的目的是确定调强质子治疗（IMPT）优化技术对用于计算衰减的商用磁共振图像（MRCA T）、基于磁共振成像（MRI）扫描的合成计算机断层扫描CT（sCT）与CT图像的质子剂量比较的影响，并找出能生成与常规CT图像集剂量差异最小的计划的优化技术。
本研究获取了10例前列腺癌患者的常规CT数据集和sCT图像集。使用六种不同的IMPT优化技术在CT图像集中创建了六个计划，包括多野优化（MFO）、单野均匀剂量（SFUD）优化和稳健优化（RO）。将这些计划复制到MRCA T、sCT数据集中并计算剂量。使用二维剂量分布显示、剂量体积直方图（DVH）、均匀性指数（HI）、适形数（CN）和三维伽马分析对每位患者的CT和MRCA T数据集的剂量进行比较。对HI和CN进行双尾t检验，显著性水平为5%，原假设为CT和sCT图像集。
对采用不同IMPT优化技术的十个CT和sCT图像集进行分析表明，部分技术在一些评估参数的计划之间显示出显著差异。等剂量线、DVH、HI、CN和t检验分析表明，纳入2%范围误差的稳健优化生成的计划，在sCT图像集中重新计算时，与其他优化技术相比，与CT计划的剂量差异最小。剂量差异次小的优化技术是纳入5%范围误差的稳健优化。
本研究肯定地证明了IMPT优化技术对合成CT图像集与CT图像的剂量比较的影响，并确定纳入2%范围误差的稳健优化是与CT计划相比剂量差异最小的优化技术。
