Parenchymal CSF Fraction and DTI‐ALPS in Brain Aging

Abstract

AbstractBackgroundThe perivascular space (PVS) functions as part of a brain clearance system that drains interstitial fluid and solutes including Aβ and tau from brain parenchyma and is associated with the development of AD. Recent developed imaging tools of cerebral parenchymal CSF fraction (CSFF)1 and diffusion tensor imaging along perivascular spaces index (DTI‐ALPS)2 provide an insight of the perivascular CSF flow and early PVS pathology in the cerebral cortex. We applied CSFF and DTI‐ALPS in an elderly cognitive normal cohort to investigate its value in brain aging.MethodA total of 27 cognitive normal subjects in this study are within age 57 and 82 years (mean=67.7, std=6.4). We conducted MR FASTT2 scan for CSFF, T1W, T2W for PVS burden, and DTI for DTI_ALPS index. CSFF was fitted using three compartment model with 6 TEs = 0, 7.5, 17.5, 67.5, 147.5, 307.5 ms. PVS burden was calculated by using imaging processing based PVS segmentation on enhance PVS image (T2W/T1W). DTI_ALPS was calculated by mean(D𝑥_𝑝𝑟𝑜𝑗,D𝑥_𝑎𝑠𝑠𝑜𝑐)/mean (D𝑦_𝑝𝑟𝑜𝑗, D𝑧_𝑎𝑠𝑠𝑜𝑐), where Dx, Dy and Dz are the diffusivity along x‐, y‐ and x‐axis, and the projection, association regions. Multi‐variate linear model Age∼1+DTI_ALPS+CSFF was compared with Age∼1+DTI_ALPS+PVS_burden.ResultFigure 1 (a) and (b) show the PVS mask on T2W and CSFF map. Figure 2 shows the scattered plot of linear model between age and PVS burden+DTI_ALPS, which is not significant (p=0.06, R2=0.14). Figure 3 is the plot of the model between age and CSFF+DTI_ALPS, which is significant (p<0.01, R2=0.34).ConclusionThe preliminary results showed CSFF and DTI‐ALPS can better predict brain aging. The conventional PVS burden only measures the MRI visible PVS in brain white matter while CSFF can assess micro‐scale PVS along small arteriole and capillary in the cerebral cortex, which is closely related to glymphatic system and may reflect the PVS function alert at early stage. CSFF and DTI‐ALPS could be a potential marker for detecting early stage of dysfunction of glymphatic clearance. Reference: 1. Liangdong Zhou, BioRvix:2021.02.01.429067, 2021. 2. Toshiaki Taoka, Jpn.J.Radiol. 2022;40:147–58.3.