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

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 midthigh 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.

Moderate‐to‐Vigorous Physical Activity Is Associated With Higher Muscle Oxidative Capacity in Older Adults

“…Indeed, this result remains important because it demonstrates that, although MVPA is strongly associated with muscle oxidative capacity, some other unknown effects of age negatively affect mitochondrial function via mechanisms that are not fully offset by higher levels of MVPA. 3,28,29 These findings contrast with previously published results, suggesting that the decline in mitochondrial function with aging is explained by an age-associated reduction of physical activity. 8,11 This discrepancy may be due to the small sample size of fewer than 40 participants in these previous studies.…”

Demonstration of asymmetric muscle perfusion of the back after exercise in patients with adolescent idiopathic scoliosis using intravoxel incoherent motion (IVIM) MRI

“…However, the IVIM method only permits a reduced temporal resolution and the repeated measures are probably limited to more strenuous challenges to elicit persistent hyperemia for functional studies. An increase in f following exercise compared with baseline could be observed for up to 10 min in the masticator muscle and even up to 20 min in the forearm and the thigh . In another study, IVIM parameters reverted to resting values within 3 min in the calf .…”

“…An increase in f following exercise compared with baseline could be observed for up to 10 min in the masticator muscle 22 and even up to 20 min in the forearm 24 and the thigh. 26 In another study, IVIM parameters reverted to resting values within 3 min in the calf. 27 These differences might be due to different exercise intensities.…”

“…Of the eight patients with AIS (all females; mean ± standard deviation [range] 32 ± 12 [17‐47] years old), seven exhibited a standard thoracic right, lumbar left convex scoliosis with a thoracic Cobb angle of 35° ± 10° [25°‐47°] and a lumbar Cobb angle of 28° ± 10° [15°‐41°], and one exhibited an atypical right convex lumbar scoliosis with a Cobb angle of 30° (Table ). The control group was made up of nine healthy volunteers (seven females and two males; 25 ± 1 years old). All patients and volunteers successfully performed the Roman chair exercise, and exhaustion was reached after 1 min 15 s ± 21 s [48 s‐1 min 40 s] in the AIS patients, and after 1 min 37 s ± 22 s [1 min 5 s‐2 min 3 s] in the healthy volunteers ( p < 0.05).…”

“…[14][15][16][17] Perfusion imaging is thought to be the best technique for accurately assessing muscle energy consumption, 18 and could therefore be used to study non-invasively muscular activation patterns. Intravoxel incoherent motion (IVIM) is a magnetic resonance perfusion imaging technique that extracts local perfusion information from a multi-b-value diffusion-weighted sequence, 19 and can be used for quantitative muscular perfusion imaging, [20][21][22][23][24][25][26][27][28] with a high resolution and large field of view compared with methods such as electromyography or ultrasound, permitting a detailed analysis of the muscular perfusion pattern. A Roman chair is a piece of equipment to exercise back flexion and extension and induces suitably well localized muscle activation.…”