Regional changes in cerebral perfusion with age when accounting for changes in gray-matter volume

Abstract

Purpose: One possible contributing factor for cerebral blood flow (CBF) decline in normal aging is the increase in partial volume effects due to brain atrophy, as cortical thinning can exacerbate the contamination of gray-matter (GM) voxels by other tissue types. This work investigates CBF changes in normal aging of a large elderly cohort aged 54 to 84 and how correction for partial volume effects that would accommodate potential changes in GM might affect this.

Methods: The study cohort consisted of 474 participants aged 54 to 84 years using pseudo-continuous arterial spin labeling MRI. A volumetric pipeline and a surface-based pipeline were applied to measure global and regional perfusion. Volumetric regions of interest (ROIs) included GM, cerebral white matter, vascular territories, and the brain atlas from the UK Biobank. The cortical parcellation was using Desikan-Killiany atlas. Non-partial volume effect correction (PVEc) and PVEc GM-CBF changes with aging were modeled using linear regressions.

Results: Global GM CBF decreased by 0.17 mL/100 g/min per year with aging before PVEc (p < 0.05) and was 0.18 mL/100 g/min after PVEc (p < 0.05). All cortical parcels exhibited CBF decreases with age before PVEc. After PVEc, seven parcels retained decreasing trends. However, GM CBF demonstrated increase with age after PVEc in three parcels.

Conclusion: Although decreases in global perfusion are observed with aging before PVEc, perfusion variations appear to be more regionally selective after PVEc. This supports the understanding that variation in cerebral perfusion with age observed with imaging is influenced by regional changes in anatomy that can be accommodated with PVEc, but perfusion variation is still observable even after PVE is accounted for.

Keywords: arterial spin labeling; brain atrophy; partial volume effects correction; perfusion; surface‐based analysis.

FIGURE 1

Top and bottom: Arterial spin labeling (ASL) surface‐based pipeline and ASL volumetric pipelines, respectively. Middle: T₁‐weighted (T1w) processing pipeline. HCP, Human Connectome Project; PV partial volume; PVEc, partial volume effect correction.

FIGURE 2

Partial volume estimates from FSL FAST (top) cerebrospinal fluid and from Toblerone (bottom). 1(a), 2(a): Gray matter. 1(b), 2(b): White matter. 1(c): Cerebrospinal fluid.

FIGURE 3

Non–partial volume effect correction (PVEc) arterial spin labeling (ASL) image (left) and PVEc ASL image (right) from the same subject in the standard space projected onto the 32k_fs_LR cortical midthickness surface. CBF, cerebral blood flow.

FIGURE 4

Atlases and regions of interest (ROIs) used in volumetric analysis. (A) Cerebral white matter. (B) Vascular territories (right internal carotid artery territory, left internal carotid artery territory, and vertebrobasilar arteries territory). (C) Eighteen ROIs used in UK Biobank in the standard space, including caudate, cerebellum, frontal lobe, insula, occipital lobe, parietal lobe, putamen, temporal lobe, and thalamus.

FIGURE 5

Age‐related gray‐matter (GM) cerebral blood flow (CBF) changes by sex and with/without partial volume effect correction (PVEc). Top row: Non‐PVEc results. Bottom row: PVEc results. The age‐related normative values for GM CBF are displayed across the 5th, 10th, 25th, 50th, 75th, 90th, and 95th percentiles from low to high. The decreasing trends were significant in males but not in females.