COMPARISON OF BONE-DENSITY MEASUREMENT TECHNIQUES - DXA AND ARCHIMEDES PRINCIPLE

The standard method for determination of density (g/cm(3)) of bones fr om small animals has been the application of Archimedes' principle, A recent development has been software for the determination of ''densit y'' (g/cm(2)) of small animal bones with dual-energy X-ray absorptiome try (DXA), We compared Archimedes' principle and DXA (Hologic QDR-2000 ) in the measurement of the densities of whole and hollowed femurs of 5- to 6-month-old retired female breeder rats, In an attempt to ensure detectable treatment differences, rats were used from a low-vitamin D Holtzman and a supplemental-vitamin I) Sprague-Dawley colony, Whole f emur densities were higher for supplemental-vitamin D colony rats than for low vitamin D rats using both techniques (Archimedes' principle, p < 0.002; DXA, p < 0.005), and the densities from the two techniques were highly correlated (r = 0.82, p < 0.0001), Actual density values w ere higher for Archimedes' principle than for DXA, Other variables suc h as femur ash weight and calcium content were also highly correlated to densities with both techniques, Hollowed femur density values were higher than whole femur values with Archimedes' principle but lower wi th DXA, Colony effects for hollowed femur densities were diminished wi th Archimedes' principle (p < 0.03) and eliminated,vith DXA (p < 0.53) , Investigation of whole bones is more biologically relevant, and both techniques were effective in detecting differences between whole femu rs from low-vitamin D and supplemental-vitamin D colony rats.