Mitsuyoshi Takamasa, Nakamura Mitsuhiro, Matsuo Yukinori, Ueki Nami, Nakamura Akira, Iizuka Yusuke, Mampuya Wambaka Ange, Mizowaki Takashi, Hiraoka Masahiro
Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Med Dosim. 2016;41(4):305-309. doi: 10.1016/j.meddos.2016.07.003. Epub 2016 Sep 10.
The purpose of this article is to quantitatively evaluate differences in dose distributions calculated using various computed tomography (CT) datasets, dose-calculation algorithms, and prescription methods in stereotactic body radiotherapy (SBRT) for patients with early-stage lung cancer. Data on 29 patients with early-stage lung cancer treated with SBRT were retrospectively analyzed. Averaged CT (Ave-CT) and expiratory CT (Ex-CT) images were reconstructed for each patient using 4-dimensional CT data. Dose distributions were initially calculated using the Ave-CT images and recalculated (in the same monitor units [MUs]) by employing Ex-CT images with the same beam arrangements. The dose-volume parameters, including D, D, D, and D of the planning target volume (PTV), were compared between the 2 image sets. To explore the influence of dose-calculation algorithms and prescription methods on the differences in dose distributions evident between Ave-CT and Ex-CT images, we calculated dose distributions using the following 3 different algorithms: x-ray Voxel Monte Carlo (XVMC), Acuros XB (AXB), and the anisotropic analytical algorithm (AAA). We also used 2 different dose-prescription methods; the isocenter prescription and the PTV periphery prescription methods. All differences in PTV dose-volume parameters calculated using Ave-CT and Ex-CT data were within 3 percentage points (%pts) employing the isocenter prescription method, and within 1.5%pts using the PTV periphery prescription method, irrespective of which of the 3 algorithms (XVMC, AXB, and AAA) was employed. The frequencies of dose-volume parameters differing by >1%pt when the XVMC and AXB were used were greater than those associated with the use of the AAA, regardless of the dose-prescription method employed. All differences in PTV dose-volume parameters calculated using Ave-CT and Ex-CT data on patients who underwent lung SBRT were within 3%pts, regardless of the dose-calculation algorithm or the dose-prescription method employed.
本文旨在定量评估在早期肺癌患者的立体定向体部放疗（SBRT）中，使用各种计算机断层扫描（CT）数据集、剂量计算算法和处方方法所计算出的剂量分布差异。对29例接受SBRT治疗的早期肺癌患者的数据进行了回顾性分析。利用四维CT数据为每位患者重建平均CT（Ave-CT）图像和呼气CT（Ex-CT）图像。最初使用Ave-CT图像计算剂量分布，并通过采用相同射束排列的Ex-CT图像（在相同的监测单位[MUs]下）重新计算剂量分布。比较了两个图像集之间计划靶区（PTV）的剂量体积参数，包括D、D、D和D。为了探究剂量计算算法和处方方法对Ave-CT和Ex-CT图像之间明显的剂量分布差异的影响，我们使用以下3种不同算法计算剂量分布：X射线体素蒙特卡罗（XVMC）、Acuros XB（AXB）和各向异性分析算法（AAA）。我们还使用了2种不同的剂量处方方法；等中心处方和PTV周边处方方法。无论采用3种算法（XVMC、AXB和AAA）中的哪一种，使用等中心处方方法时，利用Ave-CT和Ex-CT数据计算出的PTV剂量体积参数的所有差异均在3个百分点（%pts）以内，而使用PTV周边处方方法时则在1.5%pts以内。无论采用何种剂量处方方法，使用XVMC和AXB时剂量体积参数相差>1%pt的频率均高于使用AAA时的频率。无论采用何种剂量计算算法或剂量处方方法，对接受肺部SBRT治疗的患者利用Ave-CT和Ex-CT数据计算出的PTV剂量体积参数的所有差异均在3%pts以内。
