Quantification of Vertebral Bone Marrow Fat Content Using 3 Tesla MR Spectroscopy: Reproducibility, Vertebral Variation, and Applications in Osteoporosis

Purpose: To determine the reproducibility of proton MR spectroscopy ((1)H-MRS) for assessing vertebral bone marrow adiposity at 3 Tesla (T); to evaluate variation of marrow adiposity at different vertebral levels; and to demonstrate the feasibility of using (1)H-MRS at 3T for evaluating marrow adiposity in subjects with low bone density. Materials and Methods: Single voxel MRS was acquired at vertebral body L1 to L4 at 3T in 51 postmenopausal females including healthy controls (n = 13) and patients with osteoporosis/osteopenia (n = 38). Marrow fat contents were compared between vertebral levels and between groups using analysis of variance (ANOVA). Six subjects were scanned twice to evaluate technique reproducibility. Results: The average coefficient of variation of vertebral marrow fat content quantification was 1.7%. Marrow fat content significantly increased from L1 to L4. The average fat content was significantly elevated in patients with osteoporosis/osteopenia compared with controls, adjusted for age and body mass index (P < 0.05). Conclusion: In vivo MRS at high field strength provides reliable measurement of marrow adiposity with excellent reproducibility and can be a valuable tool for providing complementary information on bone quality and potentially also fracture risk.