MR relaxometry of lumbar spine, hip, and calcaneus in healthy premenopausal women: relationship with dual energy X-ray absorptiometry and quantitative ultrasound

This study evaluates if the reversible transverse relaxation rate (R-2') assessed in vivo by MR of lumbar vertebrae, hip, and calcaneus is correlated with dual energy X-ray absorptiometry (DXA) and to quantitative ultrasound (QUS) of the calcaneus. Fifteen healthy premenopausal women aged 23-47 years were studied by DXA, QUS, and MR relaxometry. The GESFIDE sequence was used to separate the FID rate (R-2*) into its two components, the non-reversible transverse relaxation rate (R-2) and the reversible transverse relaxation rate (R-2'). Long-term reproducibility was obtained by repeated measurements of hip and calcaneus in nine individuals after 300 +/- 59 days. R-2' and R-2* of the calcaneus had a relationship to broad-band ultrasound attenuation (BUA; r = 0.46, both p < 0.05), but not to other US or DXA parameters of the calcaneus. Both R-2' and R-2* were correlated with bone mineral per area (BMA) of the hip (r > 0.73, p < 0.001 and r > 0.66, p < 0.01, respectively). R-2 was correlated with BMA(L1-L4) (r = 0.52, p < 0.05). R-2' and R-2* were not correlated with BMA(L1-L4). When the right and left sides were compared in calcaneus and hip the correlation coefficient for R-2' and R-2* ranged from 0.76 to 0.86 (p < 0.001). The long-term reproducibility expressed in coefficient of variation (CV%) was approximately 5% for R-2 and approximately 4% for R-2*. Differences in R-2 between individuals were not reproducible. The results of this study indicate that R2' and R2* measurements are reproducible and might be of value when evaluating bone quality of the hip and foot.