Quantifying Leg Muscle Disuse Atrophy During Bed Rest Using DXA, CT, and MRI

This study evaluated whether dual-energy X-ray absorptiometry (DXA), computed tomography (CT), and magnetic resonance imaging (MRI) provide comparable outcomes in quantifying disuse-induced skeletal muscle atrophy. Although the calculation of muscle volume using MRI analysis may be considered the gold standard, the method remains labor intense and, as such, less practical and more costly. In this context, we also evaluated the efficacy of a commercially available automated MRI analysis method to measure changes in leg muscle volume after two weeks of bed rest. Twelve healthy, male adults (age: 24 ± 3 years, BMI: 23.7 ± 3.1 kg/m²) were subjected to 2 weeks of strict bed rest. Leg muscle assessments were performed before and after bed rest using DXA, single slice (thigh) CT, and MRI. MRI data analyses were performed using both a manual and automated (AMRA) method. Leg lean mass, as assessed with DXA, declined by 5% following bed rest (from 10.2 ± 1.6 to 9.7 ± 1.6 kg; p < 0.001). The thigh muscle cross-sectional area, as assessed with CT, declined by 6% following bed rest (from 155 ± 26 to 146 ± 24 cm²; p < 0.001). Muscle volume, as assessed using MRI, declined by 5% following bed rest, both when assessed manually (from 7.1 ± 1.1 to 6.7 ± 1.0 L; p < 0.001) and automatically (from 7.2 ± 1.1 to 6.8 ± 1.0 L; p < 0.001). A very strong correlation (r = 0.96; p < 0.001) with a low bias (−0.11 ± 0.29 L) was observed between manual and automated muscle volume analysis. DXA, CT, and MRI all show a ∼5% decline in leg muscle quantity following two weeks of bed rest in healthy adults. When using MRI, disuse muscle atrophy can be accurately quantified using an automated approach, rendering time-consuming manual analysis obsolete.