Multiparametric Aging Study Across Adulthood in the Leg Through Quantitative MR Imaging, 1H Spectroscopy, and 31P Spectroscopy at 3T

Background Improved characterization of healthy muscle aging is needed to establish early biomarkers in age‐related diseases. Purpose To quantify age‐related changes on multiple MRI and clinical variables evaluated in the same cohort and identify correlations among them. Study Type Prospective. Population 70 healthy subjects (30 men) from 20 to 81 years old. Field Strength/Sequence 3T/water T 2 (multiecho SE, multi‐TE STEAM), water T 1 (GRE MR Fingerprinting), fat‐fraction (multiecho GRE, multi‐TE STEAM), carnosine (PRESS), multicomponent water T 2 (ISIS‐CPMG SE train), and 31 P pulse‐acquire spectroscopy. Assessment Age‐ and sex‐related changes on: Imaging: fat‐fraction (FF MRI ), water T 1 (T 1‐H2O ), and T 2 (T 2‐H2O‐MRI ) and their heterogeneities ΔT 1‐H2O and ΔT 2‐H2O‐MRI in the posterior compartment (PC) and anterior compartment (AC) of the leg. 1 H spectroscopy: Carnosine concentration, pH, water T 2 components (T 2‐H2O‐CPMG ), fat‐fraction (FF MRS ), and water T 2 (T 2‐H2O‐MRS ) in the gastrocnemius medialis. 31 P spectroscopy: Phosphodiesters (PDE), phosphomonoesters, inorganic phosphates (Pi), and phosphocreatine (PCr) normalized to adenosine triphosphate (ATP) and pH in the calf. Clinical evaluation: Body‐mass index (BMI), gait speed (GS), plantar flexion strength, handgrip strength (HS), HS normalized to wrist circumference (HS norm ), physical activity assessment. Statistical Tests Multilinear regressions with sex and age as fixed factors. Spearman correlations calculated between variables. Benjamini–Hochberg procedure for false positives reduction (5% rate). A P < 0.05 significance level was used. Results Significant age‐related increases were found for BMI ( ρ Age = 0.04), HS norm ( ρ Age = −0.01), PDE/ATP ( ρ Age = 2.8 × 10 −3 ), Pi/ATP ( ρ Age = 2.0 × 10 −3 ), Pi/PCr ( ρ Age = 0.3 × 10 −3 ), T 2‐H2O‐MRS ( ρ Age = 0.051 msec), FF MRS ( ρ Age = 0.036) the intermediate T 2‐H2O‐CPMG component time ( ρ Age = 0.112 msec), and fraction ( ρ Age = −0.3 × 10 −3 ); and in both compartments for FF MRI ( ρ Age = 0.06, PC; ρ Age = 0.06, AC), T 2‐H2O‐MRI ( ρ Age = 0.05, PC; ρ Age = 0.05, AC; msec), ΔT 2‐H2O‐MRI ( ρ Age = 0.02, PC; ρ Age = 0.02, AC; msec), T 1‐H2O ( ρ Age = 1.08, PC; ρ Age = 1.06, AC; msec), and ΔT 1‐H2O ( ρ Age = 0.22, PC; ρ Age = 0.37, AC; msec). The best age predictors, accounting for sex‐related differences, were HS norm ( R 2 = 0.52) and PDE/ATP ( R 2 = 0.44). In both leg compartments, the imaging measures and HS norm were intercorrelated. In PC, T 2‐H2O‐MRS and FF MRS also showed numerous correlations to the imaging measures. PDE/ATP correlated to T 1‐H2O, T 2‐H2O‐MRI , ΔT 2‐H2O‐MRI , FF MRI , FF MRS , the intermediate T 2‐H2O‐CPMG , BMI, Pi/PCr, and HS norm . Data Conclusion Our multiparametric MRI approach provided an integrative view of age‐related changes in the leg and revealed multiple correlations between these parameters and the normalized HS. Level of Evidence 1 Technical Efficacy Stage 3