磁共振非高斯弥散加权成像评价健康脑白质和脑胶质瘤水弥散微环境的可重复性研究

Evaluation of water diffusion microenvironment in healthy brain white matter and gliomas using non-Gaussian diffusion MR imaging: a reproducibility study

目的 探讨磁共振22b值（0-5000 s/mm2）非高斯弥散加权成像在健康成人脑白质和胶质瘤应用的可重复性。方法 12名健康志愿者和65名胶质瘤患者进行22 b值e DWI（enhanced diffusion weighted imaging）磁共振扫描。前者进行连续2次e DWI扫描,选取基底节层面和半卵圆中心层面深部白质为感兴趣区;后者进行单次e DWI扫描,由2名神经放射医师分别在肿瘤最大层面的肿瘤实质区放置感兴趣区,工作站进行双指数和拉伸指数模型后处理;前者对2次扫描双指数模型拟合的慢弥散系数Dslow（slow diffusion coefficient）、快弥散系数Dfast（fast diffusion coefficient）和快弥散容积分数PF（perfusion fraction of Dfast）以及拉伸指数模型拟合的分布弥散系数DDC（distributed diffusion coefficient）和不均质指数α进行配对t检验、计算变异系数（coefficient of variability,CV）和绘制BlandAltman（B-A）散点图;后者对2次测量的Dslow、Dfast、PF、DDC和α进行观察者间一致性检验,并计算CV。结果 健康志愿者各参数2次测量配对比较差异均无统计学意义（P〉0.05）,CV值均小于5%,B-A散点图绝大多数（≥11/12）测值均位于95%一致性范围内;胶质瘤各参数2次测量一致性系数均大于0.75（P〈0.001）,Dfast和PF的CV值最大,范围在5.0%-11.5%之间,其次是DDC和Dslow,α最小,CV值小于2%,除α外,其余参数CV值均随胶质瘤级别增高而增大。结论 健康脑白质评价中非高斯弥散加权成像各参数均具有较好的可重复性;胶质瘤评价中拉伸指数模型α具有最好的可重复性。

Objective To explore the reproducibility of non-Gaussian diffusion MR imaging using bi- and stretched-exponential models with 22 b-value （0 - 5 000 s/mm2） in evaluation of water diffusion microenvironment in the healthy brain white matter and gliomas. Methods Twelve healthy volunteers and 65 patients with pathologically confirmed glioma were recruited for this study. For the healthy volunteers, 2 consecutive enhanced diffusion weighted imaging （eDWI） scans were performed and post-processed using bi- and stretched-exponetial models, respectively. The white matter located at the basal ganglion and semioval centrum was selected for the placement of region of interest （ ROI）, with each section containing 4 different ROIs. For the glioma group, eDWI scan was done once. The representative section showing the largest solid tumor was identified and the tumor ROIs were delineated manually twice by two neuroradiologists separately.Mean values of slow- and fast-diffusion coefficients （ Dslow and Dfast）, perfusion fraction （ PF）, distributed diffusion coefficient （DDC） and intravoxel heterogeneity index α were calculated. The repeatability of these parameters obtained from 2 scans in healthy controls was analyzed by paired t test, coefficient of variability （CV） and Bland-Airman （B-A） plots. Analyses of intraclass correlative coefficient （ICC） and CV were used for testing the agreement of 2 scans of measurement in the same patient with glioma. Results For the 12 healthy volunteers, no significant differences in all diffusion parameters were shown between the 2 scans （P 〈0. 05）. The CV values of all parameters were below 5%. B-A plots illustrated a majority （≥11/12） of data points within 95% normalized difference for all parameters of eight ROIs in the 2 sections. For 65 cases of gliomas, satifactory agreements were acquired for all the parameters with the ICC value of more than 0.75 （P 〈0. 001）. Dfast and PF had higher CV values within a range of 5.0% - 11.5% , followed by DDC and Dslow. Their CV values were positively associated with the increasing gliomas grade. The α index had the smallest CV value of less than 2%. Conclusion Our study shows a good reproducibility of non-Gaussian derived diffusion parameters for the evaluation of water diffusion microenvironment in the healthy brain white matter, whereas the index α has the best reproducibility among the non-Gaussian derived diffusion parameters in the application of gliomas.