Comparison of synchrotron radiation and conventional x-ray microcomputed tomography for assessing trabecular bone microarchitecture of human femoral heads

Microcomputed tomography (mu CT) produces three-dimensional (3D) images of trabecular bone. We compared conventional mu CT (C mu CT) with a polychromatic x-ray cone beam to synchrotron radiation (SR) ACT with a monochromatic parallel beam for assessing trabecular bone microarchitecture of 14 subchondral femoral head specimens from patients with osteoarthritis (n = 10) or osteoporosis (n = 4). SR mu CT images with a voxel size of 10.13 Am were reconstructed from 900 2D radiographic projections (angular step, 0.2 degrees). C mu CT images with a voxel size of 10.77 Am were reconstructed from 205, 413, and 825 projections obtained using angular steps of 0.9 degrees, 0.45 degrees, and 0.23 degrees, respectively. A single threshold was used to binarize the images. We computed bone volume/tissue volume (BV/TV), bone surface/bone volume (BS/BV), trabecular number (Tb.N), trabecular thickness (Tb.Th and Tb.Th*), trabecular spacing (Tb.Sp), degree of anisotropy (DA), and Euler density. With the 0.9 degrees angular step, all C mu CT values were significantly different from SR mu CT values. With the 0.23 degrees and 0.45 degrees rotation steps, BV/TV, Tb.Th, and BS/BV by C mu CT differed significantly from the values by SR mu CT. The error due to slice matching (visual site matching 10 slices) was within 1% for most parameters. Compared to SRACT, BV/TV, Tb.Sp, and Tb.Th by C mu CT were underestimated, whereas Tb.N and Tb.Th* were overestimated. A Bland and Altman plot showed no bias for Tb.N or DA. Bias was -0.8 +/- 1.0%, +5.0 +/- 1.1 mu m, -5.9 +/- 6.3 mu m, and -5.7 +/- 29.1 mu m for BV/TV, Th.Th*, Tb.Th, and Tb.Sp, respectively, and the differences did not vary over the range of values. Although systematic differences were noted between SR mu CT and CACT values, correlations between the techniques were high and the differences would probably not change the discrimination between study groups. CACT provides a reliable 3D assessment of human defatted bone when working at the 0.23 degrees or 0.45 degrees rotation step; the 0.9 degrees rotation step may be insufficiently accurate for morphological bone analysis. (c) 2006 American Association of Physicists in Medicine.