Effects of trabecular bone on marrow relaxation in the tibia

The effects of bone on marrow relaxation in the trabecular volume of the mo st proximal 3 cm in the left tibia were studied with a RF-spoiled gradient echo MRI protocol on a 1.0 T MR unit, The MR measurements were performed on six healthy volunteers, and repeated within one month in order to assess t he precision of the method. In the same subjects, the area bone mineral den sity (BMD, g/cm(2)) was measured at the left proximal femur using dual-ener gy X-ray absorptiometry. The calcaneus of the same side was examined with q uantitative ultrasound, The marrow T2* relaxation deviated from a mono-expo nential decay, and resembled the decay of subcutaneous fat, The shape of th e relaxation curve reflected the presence of several spectral components in bone marrow, and was further influenced by the amount and structure of the surrounding trabecular bone, The bone marrow decays showed substantially r educed inter-subject variability after normalisation of the marrow data fit parameters to corresponding values for s.c. fat. This suggests the use of an internal adipose tissue reference in order to correct for diet-related v ariations of marrow T2* estimates. The mean relative precision of the MR me asurements was between 5% and 10% depending on the data ht model. Moderate- to-strong correlations between DXA BMD indices in the proximal femur and MR parameters were found (r(max) = -0.96; p < 0.01), while ultrasound-derived measures of bone strength measured on the calcaneus demonstrated significa ntly weaker correlations to the MR parameters (r(max) = -0.78; p > 0.05), T he method employed in this study showed reasonable precision and a moderate to good correlation compared to other bone parameters derived at the same extremity, and is a promising tool for the use on patients. (C) 1998 Elsevi er Science Inc.