Combined 2.25 MHz ultrasound velocity and bone mineral density measurements in the equine metacarpus and theirin vivo applications

A simple noninvasive ultrasound method is described for estimating the transverse cortical bone ultrasound velocity and the cross-sectional area of the equine third metacarpal bone (MC3). The method relies on measuring the time of flight of the ultrasound for each of two pathways, via the cortical shaft and through the central medulla. Ten metacarpal bones of approximately the same dimensions were selected to evaluate the method and to determine the practiocal correction factors Factors were established for the ovality of the external cortical boundary and the medullary cavity as well as corrections for the presence of the splint bones (second and fourth metacarpal bones, MC2 and MC4) which influence, the total cortical cross-sectional area. Conventional single-photon absorptiometry was used to measure the bone mineral content which, together with the cross-sectional area determined ultrasonically, was then used to estimate the bone mineral density. The bone mineral density was also determined for some bone sections from ash weight and volume. The compact bone density (i.e. relative density) together with the ultrasound velocity were then used to estimate a modulus of elasticity in the transverse direction.