Diffusion-weighted MRI with intravoxel incoherent motion modeling for assessment of muscle perfusion in the thigh during post-exercise hyperemia in younger and older adults

• Type of Material: Article
• Authors: Fatemeh Adelnia, National Institute on Aging; Michelle Shardell, National Institute on Aging; Christopher M. Bergeron, National Institute on Aging; Kenneth W. Fishbein, National Institute on Aging; Richard G. Spencer, National Institute on Aging; Luigi Ferrucci, National Institute on Aging; David Reiter, Emory University
• Language: English
• Date: 2019-05-01
• Publisher: Wiley
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2019 John Wiley & Sons, Inc. All rights reserved
• Final Published Version (URL): http://dx.doi.org/10.1002/nbm.4072
• Title of Journal or Parent Work: NMR in Biomedicine
• Volume: 32
• Issue: 5
• Start Page: e4072
• End Page: e4072
• Grant/Funding Information: This work was funded by the Intramural Research Program of the National Institute on Aging, National Institute of Health, Baltimore, MD, U.S.
• Keywords: IVIM modeling; Radiology, Nuclear Medicine & Medical Imaging; diffusion-weighted MRI; dynamic exercise; Technology; Shoulder; Emission computed tomography; Exercise; muscle perfusion; Skeletal muscle; Blood flow; Biophysics; Science & Technology; Rest; Life Sciences & Biomedicine; Spectroscopy; aging; thigh muscle; Monte Carlo simulation
• Research Categories: Gerontology; Biophysics, Medical; Health Sciences, Human Development; Health Sciences, Radiology

Abstract

Aging is associated with impaired endothelium-dependent vasodilation that leads to muscle perfusion impairment and contributes to organ dysfunction. Impaired muscle perfusion may result in inadequate delivery of oxygen and nutrients during and after muscle contraction, leading to muscle damage. The ability to study the relationship between perfusion and muscle damage has been limited using traditional muscle perfusion measures, which are invasive and risky. To overcome this limitation, we optimized a diffusion-weighted MRI sequence and validated an intravoxel incoherent motion (IVIM) analysis based on Monte Carlo simulation to study muscle perfusion impairment with aging during post-exercise hyperemia. Simulation results demonstrated that the bias of IVIM-derived perfusion fraction (f p ) and diffusion of water molecules in extra-vascular tissue (D) ranged from −3.3% to 14% and from −16.5% to 0.002%, respectively, in the optimized experimental condition. The dispersion in f p and D ranged from 3.2% to 9.5% and from 0.9% to 1.1%, respectively. The mid-thigh of the left leg of four younger (21–30 year old) and four older (60–90 year old) healthy females was studied using the optimized protocol at baseline and at seven time increments occurring every 3.25 min following in-magnet dynamic knee extension exercise performed using a MR-compatible ergometer with a workload of 0.4 bar for 2.5 min. After exercise, both f p and D significantly increased in the rectus femoris (active muscle during exercise) but not in adductor magnus (inactive muscle), reflecting the fact that the local increase in perfusion with both groups showed a maximum value in the second post-exercise time-point. A significantly greater increase in perfusion from the baseline (p < 0.05) was observed in the younger group (37 ± 12.05%) compared with the older group (17.57 ± 15.92%) at the first post-exercise measurement. This work establishes a reliable non-invasive method that can be used to study the effects of aging on dynamic changes in muscle perfusion as they relate to important measures of physical function.