Abstract

Background: White matter (WM) free water (FW) is likely associated with cerebral small vessel disease (CSVD). FWis the fraction of unconstrained water within an image voxel, which can be estimated from diffusion-weighted images. T2-weighted Fluid- Attenuated Inversion Recovery (FLAIR) whitematter hyperintensity (WMH)is awidely used index to assess the damages caused by CSVD. It is critical to characterize howFW content is altered inWMHlesions. In this work, we proposed a data processing framework to assess FW distributions in WMH and normal-appearingWM as well as in differentWMfiber tracts. Method: Single-shell diffusion-weighted image (SS-DWI) and T2 FLAIR image data of 133 cognitively normal (CN) adults (Table 1) were obtained from the ADNI dataset (http://adni.loni.usc.edu). FW maps were generated from SS-DWI images using the DIPY software package (https://dipy.org/). WMH lesions were identified with the lesion segmentation toolbox implemented in SPM. We co-registered FW and WMH maps of individual subjects in theMNI space. Then we derived groupWMfiber tracts using the tract-based spatial statistics (TBSS). Finally, we examined the localization of WMHandFWin the majorWMtracts.

Result: Figure 1 shows the FW map, FLAIR image, and WMH lesion from a representative subject. Figure 2 shows group average and individual FWdistributions inWMH and normal-appearingWM. Two sample T-Test found that FW content inWMH is significantly higher than that in normal-appearingWM(meanFWand standard deviation FW in WMH are 0.430 and 0.112, mean FW and standard deviation FW in normalappearingWMare 0.203 and 0.06, P < 1×10-30). TBSS based analysis showed that: 1) WMH lesions are mainly located in the corona radiata, posterior thalamic radiation, tapetum, superior fronto-occipital fasciculus, superior longitudinal fasciculus, corpus callosum, and sagittal stratum; 2) Compared with mean FWin normal-appearingWM, elevated FW content is mainly at the fornix, tapetum, cingulum hippocampus, superior fronto-occipital fasciculus, corpus callosum, sagittal stratum, and posterior thalamic radiation.

Conclusion: We developed an image processing pipeline to estimate FW changes in WMH lesions and normal-appearing WM. Free water content is elevated in WMH lesions, which is likely driven by CSVD.

Department(s)

Computer Science

Document Type

Article - Journal

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text

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English

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©2025 the Alzheimer’s Association, all rights reserved

Publication Date

2021

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