Radiology University Clinic, Coimbra University Hospital, Coimbra, Portugal.
Radiology. 2011 Sep;260(3):734-43. doi: 10.1148/radiol.11102467. Epub 2011 Jun 14.
To determine diagnostic performance of diffusion-weighted (DW) magnetic resonance (MR) imaging for assessment of complete tumor response (CR) after combined radiation therapy with chemotherapy (CRT) in patients with locally advanced rectal cancer (LARC) by means of volumetric signal intensity measurements and apparent diffusion coefficient (ADC) measurements and to compare the performance of DW imaging with that of T2-weighted MR volumetry.
A retrospective analysis of 50 patients with LARC, for whom clinical and imaging data were retrieved from a previous imaging study approved by the local institutional ethical committee and for which all patients provided informed consent, was conducted. Patients underwent pre- and post-CRT standard T2-weighted MR and DW MR. Two independent readers placed free-hand regions of interest (ROIs) in each tumor-containing section on both data sets to determine pre- and post-CRT tumor volumes and tumor volume reduction rates (volume). ROIs were copied to an ADC map to calculate tumor ADCs. Histopathologic findings were the standard of reference. Receiver operating characteristic (ROC) curves were generated to compare performance of T2-weighted and DW MR volumetry and ADC. The intraclass correlation coefficient (ICC) was used to evaluate interobserver variability and the correlation between T2-weighted and DW MR volumetry.
Areas under the ROC curve (AUCs) for identification of a CR that was based on pre-CRT volume, post-CRT volume, and volume, respectively, were 0.57, 0.70, and 0.84 for T2-weighted MR versus 0.63, 0.93, and 0.92 for DW MR volumetry (P = .15, .02, .42). Pre- and post-CRT ADC and ADC AUCs were 0.55, 0.54, and 0.51, respectively. Interobserver agreement was excellent for all pre-CRT measurements (ICC, 0.91-0.96) versus good (ICC, 0.61-0.79) for post-CRT measurements. ICC between T2-weighted and DW MR volumetry was excellent (0.97) for pre-CRT measurements versus fair (0.25) for post-CRT measurements.
Post-CRT DW MR volumetry provided high diagnostic performance in assessing CR and was significantly more accurate than T2-weighted MR volumetry. Post-CRT DW MR was equally as accurate as volume measurements of both T2-weighted and DW MR. Pre-CRT volumetry and ADC were not reliable.
通过容积信号强度测量和表观扩散系数（ADC）测量，确定扩散加权（DW）磁共振（MR）成像在接受放化疗联合治疗的局部晚期直肠癌（LARC）患者中评估完全肿瘤缓解（CR）的诊断性能，并比较 DW 成像与 T2 加权 MR 体绘制的性能。
回顾性分析了 50 例 LARC 患者的临床和影像学资料，这些资料是从之前经当地机构伦理委员会批准的影像学研究中检索出来的，所有患者均提供了知情同意。患者接受了 CRT 前后的标准 T2 加权 MR 和 DW MR。两名独立的读者在两个数据集的每个包含肿瘤的切片上放置自由手 ROI 以确定 CRT 前后的肿瘤体积和肿瘤体积减少率（体积）。ROI 被复制到 ADC 图以计算肿瘤 ADC。组织病理学发现是参考标准。生成受试者工作特征（ROC）曲线以比较 T2 加权和 DW MR 体绘制和 ADC 的性能。使用组内相关系数（ICC）评估观察者间的可变性和 T2 加权与 DW MR 体绘制之间的相关性。
基于 CRT 前体积、CRT 后体积和体积分别识别 CR 的 ROC 曲线下面积（AUC）分别为 0.57、0.70 和 0.84 用于 T2 加权 MR 与 0.63、0.93 和 0.92 用于 DW MR 体绘制（P=.15、.02、.42）。CRT 前后 ADC 和 ADC AUC 分别为 0.55、0.54 和 0.51。所有 CRT 前测量的观察者间一致性均为优秀（ICC，0.91-0.96），而 CRT 后测量的一致性为良好（ICC，0.61-0.79）。T2 加权与 DW MR 体绘制之间的 ICC 对于 CRT 前测量值为优秀（0.97），对于 CRT 后测量值为一般（0.25）。
CRT 后 DW MR 体绘制在评估 CR 方面具有较高的诊断性能，并且明显优于 T2 加权 MR 体绘制。CRT 后 DW MR 与 T2 加权和 DW MR 的体积测量一样准确。CRT 前的体积和 ADC 不可靠。
