Abstract
BackgroundAssessment of the thigh muscle fat composition using magnetic resonance imaging (MRI) can provide surrogate markers in subjects suffering from various musculoskeletal disorders including knee osteoarthritis or neuromuscular diseases. However, little is known about the relationship with muscle strength. Therefore, we investigated the associations of thigh muscle fat with isometric strength measurements.MethodsTwenty healthy subjects (10 females; median age 27 years, range 22–41 years) underwent chemical shift encoding-based water-fat MRI, followed by bilateral extraction of the proton density fat fraction (PDFF) and calculation of relative cross-sectional area (relCSA) of quadriceps and ischiocrural muscles. Relative maximum voluntary isometric contraction (relMVIC) in knee extension and flexion was measured with a rotational dynamometer. Correlations between PDFF, relCSA, and relMVIC were evaluated, and multivariate regression was applied to identify significant predictors of muscle strength.ResultsSignificant correlations between the PDFF and relMVIC were observed for quadriceps and ischiocrural muscles bilaterally (p = 0.001 to 0.049). PDFF, but not relCSA, was a statistically significant (p = 0.001 to 0.049) predictor of relMVIC in multivariate regression models, except for left-sided relMVIC in extension. In this case, PDFF (p = 0.005) and relCSA (p = 0.015) of quadriceps muscles significantly contributed to the statistical model with R2adj = 0.548.ConclusionChemical shift encoding-based water-fat MRI could detect changes in muscle composition by quantifying muscular fat that correlates well with both extensor and flexor relMVIC of the thigh. Our results help to initiate early, individualised treatments to maintain or improve muscle function in subjects who do not or not yet show pathological fatty muscle infiltration.
Highlights
Assessment of the thigh muscle fat composition using magnetic resonance imaging (MRI) can provide surrogate markers in subjects suffering from various musculoskeletal disorders including knee osteoarthritis or neuromuscular diseases
More advanced MRI-based methods including magnetic resonance spectroscopy and chemical shift encoding-based water-fat imaging enable the extraction of parameters like the proton density fat fraction (PDFF) [13, 17]
Mean muscle PDFF was lower in males than females in the left and right quadriceps muscles (2.7 ± 1.3% versus 3.6 ± 1.3%, p = 0.162; 1.7 ± 1.3% versus 2.7 ± 1.3%, p = 0.105) and ischiocrural muscles (3.2 ± 1.6% versus 4.6 ± 2.0%, p = 0.091; 2.6 ± 1.9% versus 4.9 ± 2.4%, p = 0.025; Table 1)
Summary
Assessment of the thigh muscle fat composition using magnetic resonance imaging (MRI) can provide surrogate markers in subjects suffering from various musculoskeletal disorders including knee osteoarthritis or neuromuscular diseases. Physical exercise and training have shown to entail measurable changes in the thigh musculature [10,11,12] Such alterations can nowadays be captured non-invasively by means of imaging, with magnetic resonance imaging (MRI) being at the forefront thanks to the ability to perform qualitative and quantitative assessments of the human body fat composition in vivo [13]. In contrast to conventional T1- and T2-weighted MRI, chemical shift encodingbased water-fat MRI allows for robust quantitative and, more objective evaluation of muscle composition whilst simultaneously enabling anatomical assessment [18,19,20] In this context, thigh muscles represent a region of high interest for MRI investigation thanks to good magnetic field homogeneity, minimum motion artefacts, and the knowledge about disease-characteristic features of some pathologies in these muscles. It is possible to perform precise strength measurements at thigh muscles, allowing for direct links to changes in quantitative MRI to provide insights into muscle quality and (dys-)function [21]
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