Assessment of Age‐Related Microstructure Changes in Thigh Skeletal Muscle Based on Neurite Orientation Dispersion and Density Imaging

Background Neurite orientation dispersion and density imaging (NODDI) could offer information about the morphological properties of tissue. Diffusion microstructure imaging has been widely used, but the applicability of NODDI in skeletal muscle imaging remains to be explored. Purpose To evaluate microstructure parameters variations in skeletal muscle as indicators of age‐related changes. Study Type Prospective, cross‐sectional. Population A total of 108 asymptomatic volunteers, divided into three age groups: 20–39 years ( N = 34), 40–59 years ( N = 40), and over 60 years ( N = 34). Field Strength/Sequence 3‐T, three‐dimensional (3D) gradient echo sequence. Assessment T1‐weighted imaging, T2‐weighted imaging with spectral adiabatic inversion recovery, and NODDI were used to image the thigh skeletal muscles. Four thigh skeletal muscle groups were analyzed, including bilateral thigh quadriceps femoris and hamstrings. The microstructure parameters included orientation dispersion index (ODI), intra‐myofibrillar water volume fraction (V‐intra), free‐water fraction (V‐csf), fractional anisotropy (FA), and mean diffusivity (MD). These parameters were quantified using NODDI images and compared among different age, body mass index (BMI), and skeletal muscle index (SMI) subgroups. Statistical Tests Segmentation measurement reliability was assessed using a two‐way mixed intraclass correlation coefficient (ICC). Shapiro–Wilk tests were used to assess data distribution. Kruskal–Wallis and Mann–Whitney U tests were used to compare ODI, V‐intra, V‐csf, FA, and MD values among different age, BMI, and SMI subgroups. The Spearman correlation coefficient was utilized to assess the strength of the correlation between the age and microstructure parameters, as well as between age and SMI. Additionally, Bonferroni post hoc tests were conducted on microstructure parameters that exhibited significant differences across various age groups. A P ‐value <0.05 was considered statistically significant. Results Significant differences in ODI, V‐csf, FA, and MD values were observed among age, BMI, and SMI subgroups. Data Conclusion NODDI may be used to reveal information about microstructure integrity and local physiological changes of thigh skeletal muscle fibers in relation to age. Level of Evidence 2 Technical Efficacy Stage 2