弥散梯度方向数目对DTI测量值的影响

目的 探讨弥散张量成像(DTI)中不同数目的梯度方向对成人脑组织各向异性分数(FA)的离散程度及其信噪比(SNR)的影响.方法 应用7种不同弥散梯度方向数目(NDGD)对8名健康志愿者脑组织进行DTI扫描并获取FA图,计算FA图中4个感兴趣区(ROI)(胼胝体膝部、胼胝体压部、内囊膝部、内囊后肢)的FA值及其SNR,分析其随NDGD增加的变化趋势.结果 脑内各个ROI的FA值不随NDGD的增加而显著变化;信号强的ROI(胼胝体膝部、胼胝体压部)内FA值方差随机波动,其SNR增加不大;信号弱的ROI(内囊膝部、内囊后肢)内FA值方差随着NDGD的增加而逐渐减小.结论 在DTI的临床应用中,要根据检查的部位选择最适宜的NDGD.

Impact of the number of diffusion gradient directions on measuring values in diffusion tensor imaging

Objective To assess the impact of different number of diffusion gradient directions (NDGD) of diffusion tensor imaging (DTI) on dispersion degree of fractional anisotropy (FA) values and signal-to-noise ratio (SNR) for adult brain tissues. Methods Eight healthy volunteers underwent DTI with 7 NDGD respectively, and the associated FA maps were obtained. Four region of interest (ROI) (genu and splenial of corpus callosum, genu and posterior limb of internal capsule) were chosen in white matter of FA maps, FA values and the corresponding SNRs of the ROIs were computed and analyzed with NDGD increasing. Results FA values within all ROIs did not change remarkably with NDGD increasing. Variance of FA value within two ROIs with high gray value (genu and splenial of corpus callosum) fluctuated randomly and SNR increased slightly, while variance of FA value within the ROIs with low gray value (genu and posterior limb of internal capsule) diminished significantly with NDGD increasing. Conclusion In clinical applications of DTI, an optimum NDGD for DTI data acquisition should be selected according to the ROIs in human brain to be inspected.