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Abstract 37: Increased Mean Transit Time and Blood Brain Permeability in Asymptomatic White Matter Lesions of Ischemic Origin


 Introduction:
 White matter lesions of presumed ischemic origin (WMH) have been associated with increased risk of stroke, cognitive and motor decline, and are a subject of public health research. Engineering new MRI pipelines allowing for determination of mean transit time (MTT), and blood brain barrier permeability (BBBP), within WMH lesions is required for long-term population-based studies of lesion progression in patients with dementia and vascular cognitive impairment.
 
 
 Methods:
 WMH lesion volumes in 24 asymptomatic individuals was determined using an automated segmentation methodology, S3DL, with manual correction to remove false positives. A double contrast injection scheme was used to measure both K
 trans
 using dynamic contrast enhanced (DCE) imaging and K
 2
 using dynamic susceptibility contrast (DSC) imaging which also provided perfusion-related measures. BBBP was measured as k
 2
 within segmented WMH lesions and compared with normal white and gray matter.
 
 
 Results:
 The mean transit time (MTT) was found to be significantly prolonged (8.11, p<0.001Wilcoxon Signed-Rank Test) in WMH lesions when compared to normal appearing white and gray matter. There was no significant difference in DCE-K
 trans
 (0.018, p=0.351) between the lesions and the white/gray matter. Permeability measured in the WMH lesions using the DSC-K
 2
 method was increased and was correlated withincreasing total WMH lesion volume (spearman correlation 0.44; p< 0.046).
 
 
 Conclusion:
 In this first study using an advanced WMH lesion automated segmentation pipeline, we measured DCE and DSC perfusion and permeability variables within WMH lesions and compared them to normal white and grey matter in healthy people. We observed increasing MTT, within WMH lesions as compared to unaffected white and gray matter. Using the DSC-K
 2
 method, BBBP was higher within WMH lesions in these asymptomatic people, and correlated with increasing total lesion volume.
