Department of Diagnostic Radiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China.
Int J Radiat Oncol Biol Phys. 2013 Oct 1;87(2):407-13. doi: 10.1016/j.ijrobp.2013.05.026.
To improve the accuracy of volume and apparent diffusion coefficient (ADC) measurements in diffusion-weighted magnetic resonance imaging (MRI), we proposed a method based on thresholding both the b0 images and the ADC maps.
In 21 heterogeneous lesions from patients with metastatic gastrointestinal stromal tumors (GIST), gross lesion were manually contoured, and corresponding volumes and ADCs were denoted as gross tumor volume (GTV) and gross ADC (ADC(g)), respectively. Using a k-means clustering algorithm, the probable high-cellularity tumor tissues were selected based on b0 images and ADC maps. ADC and volume of the tissues selected using the proposed method were denoted as thresholded ADC (ADC(thr)) and high-cellularity tumor volume (HCTV), respectively. The metabolic tumor volume (MTV) in positron emission tomography (PET)/computed tomography (CT) was measured using 40% maximum standard uptake value (SUV(max)) as the lower threshold, and corresponding mean SUV (SUV(mean)) was also measured.
HCTV had excellent concordance with MTV according to Pearson's correlation (r=0.984, P<.001) and linear regression (slope = 1.085, intercept = -4.731). In contrast, GTV overestimated the volume and differed significantly from MTV (P=.005). ADC(thr) correlated significantly and strongly with SUV(mean) (r=-0.807, P<.001) and SUV(max) (r=-0.843, P<.001); both were stronger than those of ADC(g).
The proposed lesion-adaptive semiautomatic method can help segment high-cellularity tissues that match hypermetabolic tissues in PET/CT and enables more accurate volume and ADC delineation on diffusion-weighted MR images of GIST.
为了提高磁共振弥散加权成像（DWI）中体积和表观弥散系数（ADC）测量的准确性，我们提出了一种基于对 b0 图像和 ADC 图进行阈值处理的方法。
在 21 例转移性胃肠道间质瘤（GIST）患者的异质性病变中，手动勾画大体病变，并分别表示为大体肿瘤体积（GTV）和大体 ADC（ADC（g））。使用 k-均值聚类算法，根据 b0 图像和 ADC 图选择可能的高细胞肿瘤组织。使用所提出的方法选择的 ADC 和体积的组织分别表示为阈值 ADC（ADC（thr））和高细胞肿瘤体积（HCTV）。正电子发射断层扫描（PET）/计算机断层扫描（CT）中的代谢肿瘤体积（MTV）使用 40%最大标准摄取值（SUV（max））作为下限进行测量，同时也测量了相应的平均 SUV（SUV（mean））。
HCTV 与 MTV 根据 Pearson 相关（r=0.984，P<.001）和线性回归（斜率=1.085，截距=-4.731）具有极好的一致性。相比之下，GTV 高估了体积，与 MTV 有显著差异（P=.005）。ADC（thr）与 SUV（mean）（r=-0.807，P<.001）和 SUV（max）（r=-0.843，P<.001）均呈显著相关，且相关性较强；两者均强于 ADC（g）。
提出的病变自适应半自动方法可以帮助勾画与 PET/CT 中高代谢组织相匹配的高细胞组织，并在 GIST 的 DWI 磁共振图像上实现更准确的体积和 ADC 勾画。
