Changes in lumbar muscle diffusion tensor indices with age

Area of Science:

• Biomedical Engineering
• Radiology
• Musculoskeletal Imaging

Background:

• Age-related changes in skeletal muscle composition and microstructure are not fully understood.
• Previous studies on aging and spinal muscles have limitations in sample size and age group separation.
• Diffusion Tensor Imaging (DTI) and Proton Density Fat Fraction (PDFF) offer sensitive measures of tissue microstructure and composition.

Purpose of the Study:

• To investigate age-related differences in DTI parameters and PDFF within specific lumbar spinal muscles.
• To compare DTI metrics and fat content between younger and older healthy adult males.

Main Methods:

• Recruited 12 younger (19-30 years) and 12 older (61-81 years) healthy, physically active males.
• Acquired T1w, T2w, Dixon, and DTI of the lumbar spine.
• Quantified DTI eigenvalues (λ1, λ2, λ3), fractional anisotropy (FA), mean diffusivity (MD), and PDFF in multifidus, erector spinae (medial and lateral), and quadratus lumborum muscles.
• Utilized two-way ANOVA and t-tests to analyze age and muscle group differences.

Main Results:

• Significant age-related differences were observed for all DTI parameters and PDFF (P < .01).
• Older males exhibited lower mean eigenvalues and MD, and higher FA compared to younger males.
• Statistical significance for these DTI changes was noted in the lateral erector spinae and quadratus lumborum muscles.
• Some DTI parameters (λ3, MD) showed significant age differences in the medial erector spinae muscle.

Conclusions:

• Age-related alterations in spinal muscle DTI parameters reflect changes in both intracellular and extracellular spaces.
• These microstructural changes cannot be solely attributed to variations in muscle fiber length and diameter.
• The study provides robust data on age-related spinal muscle changes using well-defined age groups.