Cross-sectional study of osteopenia with quantitative MR imaging and bone densitometry

PURPOSE: To evaluation the cancellous bone-induced intravoxel Spin dephasin g rate (R2') and;its relationship td bone mineral density and marrow fat an d to examine these parameters as predictors of vertebral fracture status. MATERIALS AND METHODS: R2' and R2, the rate constants for reversible and ir reversible spin dephasing, and marrow fat fraction were measured in the lum bar vertebrae and proximal femur. One hundred thirty-nine subjects (mean ag e, 62.4 years +/- 11.4 [SD]; 33 men, 106 women) had spinal dual-energy x-ra y absorptiometric bone mineral density (BMD)T score; ranging from +3 to -5. R2', BMD, and bone marrow composition as determinants of vertebral fractur e status were examined. RESULTS: Strongest single predictors of fracture status for BMD and R2' wer e the Ward triangle (r(2) = 0.48) and trochanter (r(2) = 0.37), respectivel y. Combined, the two parameters and sites increased fracture prediction (r( 2) = 0.62), whereas the combination of multiple BMD sites did not. Multivar iate regression involving marrow fat fraction further improved fracture sta tus prediction. R2' was correlated with BMD at all sites, although slopes d iffered by a factor of up to 2.5, which reflected differences in trabecular orientation relative to the static field. R2, the true transverse relaxati on rate, was negatively correlated with marrow fat fraction.:A non-age-rela ted increase in marrow fat fraction in osteoporosis parallels earlier findi ngs in animal models. CONCLUSION: Cancellous bone marrow R2' measured in the proximal femur provi des information, which, with BMD, improves prediction of vertebral fracture status.