10th International Bone Densitometry Workshop, Venezia Lido, Italy, 24-28 April 1994. Bone and Mineral, 25(Supplement 2):S4, April 1994.
We have used three-dimensional x-ray microtomography to measure the detailed distribution of mineral material in cancellous bone. Microtomograms are produced from rotating orthographic projections obtained with a microfocus (0.005 mm) x-ray source. The results are typically reconstructed in a 256^3 data array with each point representing a cubic voxel ranging from 5 to 100 microns in dimensino (V) (i.e., field of view from 1.25 mm to 2.5 mm). System resolution (FWHM) is approximately 2.6 x V. Certain morphologic parameters of bone architecture can be computed from these microtomograms depending on voxel size. Bone connectivity and trabecular orientation can be determined with V=100 microns. Accurate measurement of bone volume (independent of density), bone surface area, and trabecular thickness can be done with V <= 20 microns. These parameters require that the bone surface be determined from the 3D array of tomography data. Our recent results suggest that intratrabecular density can be precisely measured with V=5 microns. Radiation dose limits in-vivo application of these methods. For protocols producing microtomograms with a signal-to-noise ratio of about 50, the radiation dose is 2000 rads for a 1.25 mm object (V=5 microns), 35 rads for a 10 mm object (V=40 microns), and 5 rads for a 25 mm object (V=100 microns). Abstract