Quantitative evaluation of vertebral marrow adipose tissue in postmenopausal female using MRI chemical shift-based water-fat separation.

AIM

To investigate the feasibility of assessing vertebral marrow adipose tissue using a magnetic resonance imaging (MRI) chemical shift-based water-fat separation technique at 3 T.

MATERIAL AND METHODS

A modified Dixon technique was performed to obtain the vertebral marrow fat fraction (FF) in a study of 58 postmenopausal females (age range 49.2-77.4 years), including 24 normal bone density, 19 osteopaenia, and 15 osteoporosis as documented with dual-energy X-ray absorptiometry. The reliability of FF measurements performed by two radiologists independently was evaluated with the intraclass correlation coefficient (ICC). Ten participants were scanned twice to assess the reproducibility of FF measurements. FF values were compared between each vertebral level and between groups.

RESULTS

The mean coefficient of variation of FF measurements was 2.1%. According to the ICC, the measurements were reliable (ICC = 0.900 for normal bone density, ICC = 0.937 for osteopaenia and ICC = 0.909 for osteoporosis, p < 0.001 for all). There was an inverse association between mean FF at L1-L4 vertebrae and lumbar spine BMD (r = -0.459, p = 0.006), which remained significant even after controlling for confounders (age, height, and body weight). FF values at different vertebral levels were significantly correlated to each other (r = 0.703-0.921, p < 0.05 for all). There was a general trend toward increased marrow adiposity for more inferior vertebral bodies. Patients with osteopaenia and osteoporosis had a higher marrow fat content compared with normal bone mass after adjusting for confounders, although no significant differences in each vertebral level and average marrow fat content were found between the osteopaenia and osteoporosis groups.

CONCLUSION

Chemical shift-based water-fat separation enables the quantitation of vertebral marrow adiposity with excellent reproducibility, which appears to be a useful method to provide complementary information to osteoporosis-related research fields.