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. (12th March 2019)

• Record Type: Journal Article
• Authors: Adelnia, Fatemeh; Shardell, Michelle; Bergeron, Christopher M.; Fishbein, Kenneth W.; Spencer, Richard G.; Ferrucci, Luigi; Reiter, David A.
• Is Part Of: NMR in biomedicine. Volume 32:Number 5(2019)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2019-03-12
• Subjects: aging -- diffusion‐weighted MRI -- dynamic exercise -- IVIM modeling -- Monte Carlo simulation -- muscle perfusion -- thigh muscle; Nuclear magnetic resonance -- Periodicals; Magnetic Resonance Spectroscopy -- Periodicals; 574
• DOI: 10.1002/nbm.4072
• Languages: English
• ISSNs: 0952-3480

Abstract

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. Abstract : We optimized a diffusion‐weighted magnetic resonance imaging sequence and validated an intravoxel incoherent motion analysis to study muscle perfusion impairment with aging during post‐exercise hyperemia in the thigh muscle. We report Monte Carlo simulations showing this approach is sensitive to differences in perfusion fraction and diffusion coefficient in response to exercise that can be interpreted in the context of the physiology of aging. This method can be used to non‐invasively study dynamic exercise‐induced changes in muscle perfusion in aging.