Quantitative ultrashort echo time (UTE) magnetic resonance imaging of femoral trabecular bone in aging and osteoporosis

OBJECTIVE: To evaluate quantitative ultrashort echo time (UTE) magnetic resonance imaging (MRI) biomarkers, pore-to-matrix ratio (PMR), and matrix index (MI) for assessing trabecular bone in the proximal femur across aging and osteoporosis-related bone status. MATERIALS AND METHODS: In this prospective study, 92 female subjects (20-83 years) were classified into four groups based on age and DXA-derived T-scores: Young Normal (n = 19), Old Normal (n = 14), Osteopenia (n = 44), and Osteoporosis (n = 15). All participants underwent 3-T hip MRI using 3D dual-echo proton-density-weighted UTE (PD-UTE) and short TR adiabatic inversion recovery UTE (STAIR-UTE) sequences. Measurements were performed in the femoral head and neck by two readers. Interobserver agreement was assessed via intraclass correlation coefficients (ICC). Group differences were analyzed with the Kruskal-Wallis test and Holm-adjusted post hoc tests. Spearman correlation analysis and receiver operating characteristic (ROC) analysis were performed. RESULTS: PMR increased and MI decreased with worsening bone status. Significant differences were observed between Young Normal and all older groups (p < 0.001). PMR from the oblique-coronal total femoral head differentiated Old Normal from Osteoporosis (5.35 vs. 8.10; p < 0.05). Both PMR (ρ = -0.406 to -0.211) and MI (ρ = 0.333-0.402) significantly correlated with T-scores (all p < 0.05). The areas under the ROC curve were 0.776 (95% CI, 0.584-0.909) for PMR and 0.738 (95% CI, 0.548-0.886) for MI. Interobserver reproducibility was substantial to almost perfect (ICC: 0.73-0.99). CONCLUSION: PMR and MI demonstrated measurable differences across age and bone status and may provide complementary information on trabecular bone characteristics. KEY POINTS: Question Can ultrashort echo time (UTE) MRI biomarkers address the need for radiation-free assessment of age- and osteoporosis-related trabecular bone changes in the proximal femur? Findings Pore-to-matrix ratio (PMR) increased and matrix index (MI) decreased with aging and worsening bone status, and femoral head PMR differentiated osteoporosis from normal bone. Clinical relevance UTE-MRI-derived PMR and MI may provide radiation-free, complementary information to dual-energy X-ray absorptiometry for assessing trabecular bone changes associated with aging and osteoporosis.