Visual estimation of vertebral marrow fat on lumbar MRI as a screening tool for osteoporosis: A retrospective study

Osteoporosis is the most common metabolic bone disease in the elderly. This study aimed to assess whether routine T1-weighted MR images can visually indicate the presence of osteoporosis by estimating vertebral bone marrow fat content.

Lumbar spine MRI and DEXA scans from 320 patients (performed within a 6-month interval) were retrospectively reviewed. Two radiologists independently graded the percentage of high T1 signal within the L4 vertebral body into <50 % or ≥50 %, representing marrow fat content. Visual fat scores were compared with T-scores from DEXA scans. Inter-reader agreement was assessed using Cohen's and Fleiss' kappa statistics. Spearman's correlation was used to evaluate the association between MRI grading and DEXA scores.

Of the 320 patients (mean age 56.8 years; 80.3 % female), 48.4 % had osteopenia or osteoporosis. Visual MRI grading yielded 141 patients with <50 % and 179 with ≥50 % marrow fat. A weak but statistically significant correlation was observed between MRI visual fat scores and DEXA T-scores (ρ = 0.139, p = 0.013). Inter-reader agreement was moderate (Cohen's kappa = 0.509, 95 % CI: 0.415 to 0.603).

Routine T1-weighted lumbar spine MRI may serve as an opportunistic screening tool for osteoporosis. Visual estimation of vertebral marrow fat content shows potential to identify patients who may benefit from further DEXA evaluation.