Assessment of Osteoporosis at the Lumbar Spine Using Ultrashort Echo Time Magnetization Transfer (UTE‐MT) MRI

Background Bone collagen‐matrix contributes to the mechanical properties of bone by imparting tensile strength and elasticity, which can be indirectly quantified by ultrashort echo time magnetization transfer ratio (UTE‐MTR) to assess osteoporosis. Purpose To evaluate osteoporosis at the human lumbar spine using UTE‐MTR. Study Type Prospective. Population One hundred forty‐eight‐volunteers (age‐range, 50–85; females, N = 90), including 81‐normal bone density, 35‐osteopenic, and 32‐osteoporotic subjects. Ten additional healthy volunteers were recruited to study the intrasession reproducibility of the UTE‐MT. Field Strength/Sequence 3T/UTE‐MT, short repetition‐time adiabatic inversion recovery prepared UTE (STAIR‐UTE), and iterative decomposition of water‐and‐fat with echo‐asymmetry and least‐squares estimation (IDEAL‐IQ). Assessment Fracture risk was calculated using Fracture‐Risk‐Assessment‐Tool (FRAX). Region‐of‐interests (ROIs) were delineated on the trabecular area in the maps of bone‐mineral‐density, UTE‐MTR, collagen‐bound water proton‐fraction (CBWPF), and bone‐marrow fat fraction (BMFF). Statistical Tests Linear‐regression and Bland–Altman analysis were performed to assess the reproducibility of UTE‐MTR measurements in the different scans. UTE‐MTR and BMFF were correlated with bone‐mineral‐density using Pearson's regression and with FRAX scores using nonlinear regression. The abilities of UTE‐MTR, CBWPF, and BMFF to discriminate between the three patient subgroups were evaluated using receiver‐operator‐characteristic (ROC) analysis and area‐under‐the‐curve (AUC). Decision‐curve‐analysis (DCA) and clinical‐impact curves were used to evaluate the value of UTE‐MTR in clinical diagnosis. The DeLong test was used to compare the ROC curves. P ‐value <0.05 was considered statistically significant. Results Excellent reproducibility was obtained for the UTE‐MT measurements. UTE‐MTR strongly correlated with bone‐mineral‐density ( r = 0.76) and FRAX scores ( r = −0.77). UTE‐MTR exhibited higher AUCs (≥0.723) than BMFF, indicating its superior ability to distinguish between the three patient subgroups. The DCA and clinical‐impact curves confirmed the diagnostic value of UTE‐MTR. UTE‐MTR and CBWPF showed similar performance in correlation with bone‐mineral‐density and cohort classification. Data Conclusion UTE‐MTR strongly correlates with bone‐mineral‐density and FRAX and shows great potential in distinguishing between normal, osteopenic, and osteoporotic subjects. Evidence Level 1 Technical Efficacy Stage 2