X-ray computed tomography of the spine and hip is an established method for quantitative bone mineral measurement that resolves elements with 1-millimeter size. For bone specimens, high-resolution laboratory computed tomography systems can describe cancellous bone architecture with resolved elements of about 50 micrometers. This is sufficient to describe bone volume, trabecular thickness and orientation, and connectivity. We have recently developed a new innovative method to perform quantitative computed tomography on an individual bone trabecula with resolved elements of 1 micrometer. Whole trabeculae are separated from cancellous bone specimens and scanned in a 250 micrometer diameter saline filled tube. A beam of x-rays from a synchrotron source is focused using a zone plate and used to make numerous measurements of radiation transmission. The measured data is then reconstructed to a 600 x 600 x 540 array of values having a spacing of 1/3 micrometers in the X, Y, and Z direction. High speed scanning devices will be used on this project to enable examination of 16 specimens per day. This method should be extremely valuable for evaluating the microscopic properties of bone tissue with respect to the mineralization of the matrix and porosity associated with osteocyte lacunae. To establish this value, four biomedical experiments are proposed for which genetic, pharmacologic, and biomechanic variables will be used to alter the bone tissue in animals. Prior experience indicates that these models should alter the mineralization and porosity at a microscopic scale.
