Marshall Cora, Thirion Pierre, Mihai Alina, Armstrong John G, Cournane Seán, Hickey Darina, McClean Brendan, Quinn John
School of Physics, University College Dublin, Dublin, Ireland.
Beacon Hospital, Dublin, Ireland.
Adv Radiat Oncol. 2022 Jul 24;8(1):101020. doi: 10.1016/j.adro.2022.101020. eCollection 2023 Jan-Feb.
The purpose of this study was to evaluate the interobserver variability in the contouring of the gross tumor volume (GTV) on magnetic resonance (MR) imaging and computed tomography (CT) for colorectal liver metastases in the setting of SABR.
Three expert radiation oncologists contoured 10 GTV volumes on 3 MR imaging sequences and on the CT image data set. Three metrics were chosen to evaluate the interobserver variability: the conformity index, the DICE coefficient, and the maximum Hausdorff distance (HDmax). Statistical analysis of the results was performed using a 1-sided permutation test.
For all 3 metrics, the MR liver acquisition volume acquisition (MR LAVA) showed the lowest interobserver variability. Analysis showed a significant difference ( < .01) in the mean DICE, an overlap metric, for MR LAVA (0.82) and CT (0.74). The HDmax that highlights boundary errors also showed a significant difference ( = .04) with MR LAVA having a lower mean HDmax (7.2 mm) compared with CT (5.7 mm). The mean HDmax for both MR single shot fast spin echo (SSFSE) (19.3 mm) and diffusion weighted image (9.5 mm) showed large interobserver variability with MR SSFSE having a mean HDmax of 19.3 mm. A volume comparison between MR LAVA and CT showed a significantly higher volume for small GTVs (<5 cm) when using MR LAVA for contouring in comparison to CT.
This study reported the lowest interobserver variability for the MR LAVA, thus indicating the benefit of using MR to complement CT when contouring GTV for colorectal liver metastases.
本研究旨在评估立体定向消融放疗（SABR）背景下，在磁共振成像（MR）和计算机断层扫描（CT）上对结直肠癌肝转移灶的大体肿瘤体积（GTV）进行轮廓勾画时观察者间的变异性。
三名放射肿瘤学专家在3个MR成像序列和CT图像数据集上勾画了10个GTV体积。选择了三个指标来评估观察者间的变异性：符合指数、戴斯系数和最大豪斯多夫距离（HDmax）。使用单侧置换检验对结果进行统计分析。
对于所有三个指标，磁共振肝脏容积采集（MR LAVA）序列显示出最低的观察者间变异性。分析显示，作为重叠指标的平均戴斯系数在MR LAVA（0.82）和CT（0.74）之间存在显著差异（P <.01）。突出边界误差的HDmax也显示出显著差异（P = 0.04），与CT（5.7 mm）相比，MR LAVA的平均HDmax较低（7.2 mm）。磁共振单次激发快速自旋回波（SSFSE）序列（19.3 mm）和扩散加权成像序列（9.5 mm）的平均HDmax均显示出较大的观察者间变异性，其中MR SSFSE序列的平均HDmax为19.3 mm。MR LAVA和CT之间的体积比较显示，在勾画小GTV（<5 cm）时，与CT相比，使用MR LAVA进行轮廓勾画时体积显著更高。
本研究报告了MR LAVA序列的观察者间变异性最低，这表明在为结直肠癌肝转移灶勾画GTV时，使用MR补充CT的益处。
