3.0T MR弥散梯度编码方向对脑组织FA值测量的影响

目的:探讨超高场强MR下弥散张量成像中弥散梯度编码方向对脑组织弥散各向异性分数(FA)的影响。方法:使用3种不同的弥散梯度编码方向(6、13和21个)在3.0T MRI上对14名健康志愿者进行头颅弥散张量成像(DTI)。在FA图上分别测量两侧半卵圆中心、胼胝体膝部、胼胝体压部、两侧内囊、丘脑及桥脑FA值,并进行统计学分析。结果:胼胝体压部FA值最高,其次为胼胝体膝部、内囊和桥脑,丘脑FA值最低。随着弥散梯度编码方向的增加,FA图质量提高,对白质纤维束细节的显示也更清楚,尤其是对脑干结构的分辨,但成像时间延长;3种不同弥散梯度编码方向的DTI扫描方案所观察到的半卵圆中心、胼胝体膝部、胼胝体压部、内囊、丘脑及桥脑的FA值不存在统计学显著性差异。结论:超高场MRI弥散梯度编码方向数目对脑组织FA值的测量无显著性影响,在临床运用中可根据患者状况选择弥散梯度编码方向,以提高DTI检查的成功率。

The influence of the number of diffusion gradient encoding directions on fractional anisotropy measurements on 3.0T MR

Objective:To explore the effect of the number of diffusion gradient encoding direction on fractional anisotropy(FA) measurements on 3.0T MR.Methods:Diffusion tensor imaging were performed in 14 health volunteers with three different diffusion gradient encoding direction on 3.0T MR imager,the number of the diffusion gradient encoding direction was 6,13 and 21 separately.The average FA of the centrum semiovale,genu and splenium of corpous callosum,the internal capsule,thalamus and the pons in the left and right side were measured of FA map by hand draw region of interest(ROI).Results:The splenium of corpous callosum had the highest FA,the next were genu corpous callosum,the internal capsule,and the pons.The margin of the white matter tract become more clearly with the increasing of the number of gradient encoding directions,especially the detail of the brain stem.But the measured FA of the centrum semiovale,genu and splenium of corpous callosum,the internal capsule,thalamus and the pons with 6,13 and 21 diffusion gradient encoding directions showed no statically difference.Conclusion:The number of diffusion gradient encoding direction has no obvious effect of FA measurements on 3.0T MR.Selecting the number of diffusion gradient encoding direction should be accord with patient's conditions to soas improve the DTI in clinical practice.