健康人脑组织DKI的可重复性研究及梯度方向数目对可重复性的影响

Study on the Repeatability of Diffusional Kurtosis Imaging in Healthy Human Brain and the Effect of Diffusion Gradient Direction Number on the Repeatability

目的:探讨健康成人脑组织扩散峰度成像(DKI)参数模型的可重复性及不同扩散梯度方向数量(NGD)对可重复性的影响。方法:23名受试者在同一台磁共振扫描仪上行两次(每次包含15个和30个NGD序列)DKI检查,提取基于自动解剖模板的90个灰质感兴趣区(ROI)和基于约翰霍普斯金大学白质图谱的48个白质ROI的各向异性分数(FA)、平均扩散率(MD)和平均扩散峰度(MK)参数值。使用组内相关系数(ICC)和变异系数(CV)衡量两次扫描结果的-致性,采用配对t检验比较两种NGD序列的DKI三个参数测量值及可重复性的差异。结果:在15个NGD序列中,灰质和白质ROI的FA.MD、MK的平均ICC值分别为0.549、0.896、0.624和0.825、0.884、0.694,平均CV值分别为3.028%、1.671%、2.632%和1.685%、1.669%、2.098%;在30个NGD序列中,灰质和白质ROI的FA.MD、MK的平均ICC值分别为0.573.0.895、0.644和0.884、0.887、0.717,平均CV值分别为3.222%、1.676%、2.575%和1.462%、1.670%、2.018%。在全脑灰白质ROI中,与30个NGD序列相比,15个NGD序列的84.722%(61/72)ROI的FA值升高(P<0.05),41.667%(30/72)ROI的MK值降低(P<0.05);两个序列之间的MD测量值差异无统计学意义(P>0.05)。30个NGD序列的白质区域FA的可重复性优于15个NGD序列(P<0.05),而MD、MK可重复性在两种序列间无显著差异(P>0.05)。结论:在脑组织的DKI成像中,全脑灰白质MD、MK及白质区的FA参数具有较好或非常好的可重复性,并且NGD对DKI测量值和可重复性有不同程度的影响。

Purpose:To investigate the repeatability of the diffusion kurtosis imaging(DKI)parametric model in healthy adults and the effect of different number of gradient directions(NGD)on the repeatability.Methods:Twenty-three subjects underwent two DKI(containing 15 and 30 NGD sequences)examinations in the same MRI scanner,and fractional anisotropy(FA),mean diffusivity(MD)and mean kurtosis(MK)values from 90 gray matter ROIs based on automated anatomical labeling and 48 white matter ROIs based on the white matter atlas of Johns Hopkins university were extracted.Intraclass correlation coefficient(ICC)and coefficient of variation(CV)were used to measure the consistency of the two scans,and paired t-tests were used to compare the FA,MD,MK values and repeatability between the two NGD sequences.Results:In the 15 NGD sequence,the average ICC values of FA,MD and MK for gray matter and white matter ROIs were 0.549,0.896,0.624 and 0.825,0.884,0.694,and the average CV values were 3.028%,1.671%,2.632%and I.685%,1.669%,2.098%,respectively.In the 30 NGD sequence,the average ICC values of FA,MD and MK for gray and white matter ROIs were 0.573,0.895,0.644 and 0.884,0.887,0.717,and the average CV values were 3.222%,1.676%,2.575%and 1.462%,1.670%,2.018%,respectively.In the whole brain,compared with the 30 NGD sequence,the FA value of 84.722%ROIs(61/72)increased(P<0.05),while the MK value of 41.667%(30/72)ROIs decreased(P<0.05)in the 15 NGD sequence,respectively;there was no statistical significant difference about the MD values between the two NGD sequences(P>0.05).The repeatability of FA in the white matter regions of the 30 NGD sequence was better than that of the 15 NGD sequence(P<0.05),while the repeatability of MD and MK were not significantly affected by NGD(P>0.05).Conclusion:In the DKI imaging of brain tssue,MD,MK in whole brain and FA in the white matter regions have good or very good repeatability,and the NGD has a certain influence on the DKI measurements and repeatability.