Accuracy and precision of in vivo bone mineral measurements in sheep usingdual-energy X-ray absorptiometry

We evaluated the precision and accuracy of bl vice measurements of spine bo ne mineral density (BMD) and bone mineral content (BMC) in five ewes using dual-energy X-ray absorptiometry (DXA, Lunar DPX-L). The short-term ill viv a reproducibility expressed as the coefficient of variation (CV) varied fro m 0.9 to 1.6% for spine BMD and from 1 to 3.1% for spine BMC. The ex vivo m easurements, performed in 20 cm of water to simulate soft tissue thickness, correlated closely with the in viva measurements, yielding an r value of 0 .98 and 0.97 for spine BMD and BMC, respectively. The accuracy was determin ed by comparing the total BMC of each vertebra measured in vivo with the co rresponding ash weight. The correlation coefficient between the two measure ments was r = 0.98, with an accuracy error of 5.6%. We concluded that the D XA allows a precise and accurate measurement of spine bone mineral in live ewes using the methodology designed for humans.