Structural integrity of the corticospinal tract (CST) after stroke is closely linked to the degree of motor impairment. However, current methods for measurement of fractional atrophy (FA) of CST based on region of interest (ROI) are time-consuming and open to bias. Here, we used tract-based spatial statistics (TBSS) together with a CST template with healthy volunteers to quantify structural integrity of CST automatically. Two groups of patients after ischemic stroke were enrolled, group 1 (10 patients, 7 men, and Fugl-Meyer assessment (FMA) scores 50) and group 2 (12 patients, 12 men, and FMA scores = 100). CST of FAipsi, FAcontra, and FAratio was compared between the two groups. Relative to group 2, FA was decreased in group 1 in the ipsilesional CST ( ), as well as the FAratio ( ). There was no significant difference between the two subgroups in the contralesional CST ( ). Compared with contralesional CST, FA of ipsilesional CST decreased in group 1 ( ). These results suggest that the automated method used in our study could detect a surrogate biomarker to quantify the CST after stroke, which would facilitate implementation of clinical practice. 1. Introduction Diffusion tensor imaging (DTI) can delineate anatomic connectivity of white matter and evaluate tract disruption in vivo, which is increasingly used in stroke-related research [1–5]. DTI-derived parameter such as fractional anisotropy (FA) has been found to reliably reflect the microstructural status of corticospinal tract (CST) in patients with stroke [6–8]. Greater gains in motor function were related to higher FA values of ipsilesional CST, and slice-by-slice analysis of FA values along the CST demonstrated that the more the ipsilesional FA profiles of patients resembled those of healthy controls, the greater their functional improvement was [6]. Meanwhile the reverse is also true that greater loss of structural integrity of the ipsilesional CST is associated with poorer motor outcomes in patients with hemiparetic stroke [7, 8]. Despite these advances, some factors impede the uptake of these approaches. CST tracking in individual stroke is often difficult due to interruption of fibers by the infarct which can result in the unreliable morphology of the tracts. Moreover, manual placement of regions of interest (ROI) in individual patients is also problematic because of operator bias, and manual labeling is time-consuming. For these reasons, its feasibility is limited. Therefore, a fully automated method of evaluating CST is urgently needed to satisfy the translational potential of CST injury
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