目的:DTI表征组织微观结构,并提供神经健康的替代措施。回波平面成像是获取DTI的一种流行方法,但容易受到各种伪影的影响(例如,易感性,动议,和涡流),这可以通过预处理来改善。有许多可用的管道,但比较其性能的数据有限,这为本研究提供了理论基础。
方法:从健康志愿者的上肢以向上和向下的方向在3T获得DTI。数据使用(i)FSL的TOPUP和涡流进行独立校正,(ii)FSL的TOPUP,(iii)DSIStudio,(四)扭曲。DTI指标是从中位数中提取的,径向,和尺神经,并使用混合效应线性回归进行比较(在管道之间)。使用Sörenson-Dice系数计算校正的b=0图像和切片匹配的T1加权(T1w)图像的几何相似性。
结果:没有预处理,向上和向下数据集与T1w的相似系数分别为0·80和0·79。预处理将几何相似性提高了1%,管道之间没有差异。与TOPUP和Eddy相比,DSIStudio和TORTOISE产生的分数各向异性估计值降低了2%和6%,径向扩散率的估计值高出6%和13%,分别。TOPUP和涡流与TOPUP的各向异性估计没有差异,但TOPUP将径向扩散系数降低了3%。管道之间的DTI度量的一致性较差。
结论:对上肢的DTI进行预处理可以改善几何相似性,但是管道的选择会在周围神经的扩散参数估计中引入临床上重要的变异性。
OBJECTIVE: DTI characterizes tissue microstructure and provides proxy measures of nerve health. Echo-planar imaging is a popular method of acquiring DTI but is susceptible to various artifacts (e.g., susceptibility, motion, and eddy currents), which may be ameliorated via preprocessing. There are many pipelines available but limited data comparing their performance, which provides the rationale for this study.
METHODS: DTI was acquired from the upper limb of heathy volunteers at 3T in blip-up and blip-down directions. Data were independently corrected using (i) FSL\'s TOPUP & eddy, (ii) FSL\'s TOPUP, (iii) DSI Studio, and (iv) TORTOISE. DTI metrics were extracted from the
median, radial, and ulnar nerves and compared (between pipelines) using mixed-effects linear regression. The geometric similarity of corrected b = 0 images and the slice matched T1-weighted (T1w) images were computed using the Sörenson-Dice coefficient.
RESULTS: Without preprocessing, the similarity coefficient of the blip-up and blip-down datasets to the T1w was 0·80 and 0·79, respectively. Preprocessing improved the geometric similarity by 1% with no difference between pipelines. Compared to TOPUP & eddy, DSI Studio and TORTOISE generated 2% and 6% lower estimates of fractional anisotropy, and 6% and 13% higher estimates of radial diffusivity, respectively. Estimates of anisotropy from TOPUP & eddy versus TOPUP were not different but TOPUP reduced radial diffusivity by 3%. The agreement of DTI metrics between pipelines was poor.
CONCLUSIONS: Preprocessing DTI from the upper limb improves geometric similarity but the choice of the pipeline introduces clinically important variability in diffusion parameter estimates from peripheral nerves.