Trabecular structure assessment in lumbar vertebrae specimens using quantitative magnetic resonance imaging and relationship with mechanical competence

The purpose of this study was to use quantitative magnetic resonance imagin g (MRI; high-resolution [HR] and relaxometry) to assess trabecular bone str ucture in lumbar vertebrae specimens and to compare these techniques with b one mineral density (BMD) in predicting stress values obtained from mechani cal tests. Fourteen vertebral midsagittal sections from lumbar vertebrae L3 were obtained from cadavers (aged 22-76 years). HR images with a slice thi ckness of 300 mum and an in-plane spatial resolution of 117 mum(2) x 117 mu m(2) were obtained. Transverse relaxation time T'(2) distribution was measu red by using an asymmetric spin-echo (ASE) sequence. Traditional morphometr ic measures of bone structure such as apparent trabecular bone fraction (ap p. BV/TV), apparent trabecular bone number (app. Tb.N), apparent trabecular bone separation (app. Tb.Sp), and apparent trabecular bone thickness (app. Tb.Th) as well as the directional mean intercept length (MIL) were calcula ted. Additionally, BMD measurements of these sections were obtained by dual -energy X-ray absorptiometry (DXA) and biomechanical properties such as dir ectional stress values (to fracture) were determined on adjacent specimens. With the exception of T'(2), all morphological parameters correlated very well with age, BMD, and stress values (\R \ between 0.79 and 0.92). However , in the direction perpendicular to the magnetic field, T'(2) values enhanc ed the adjusted R-2 correlation value with horizontal (M/L) stress values i n addition to BMD from 0.70 to 0.91 (p < 0.05).