REGIONAL-ANALYSIS OF BONE-MINERAL DENSITY IN THE DISTAL FEMUR AND PROXIMAL TIBIA USING PERIPHERAL QUANTITATIVE COMPUTED-TOMOGRAPHY IN THE RAT IN-VIVO

The use of peripheral quantitative computed tomography (pQCT) was inve stigated for the measurement of volumetric bone mineral density (BMD) in mg . cm(-3). Two studies were undertaken. In the first study, the p recision of pQCT in vivo and ex vivo was tested at 14 weeks postovarie ctomy (OVX). In the second study, the efficacy of a standard antiresor ptive treatment, 17 beta-estradiol (E2), was tested 6 weeks post-OVX. The precision for total (compact plus trabecular) BMD was 1.3-1.9%, an d that for trabecular BMD was 2.4-2.7%. There was excellent agreement between trabecular BMD measurements in vivo and ex vivo (r = 0.91). Si gnificant reductions in trabecular BMD were observed in vivo at 14 and 6 weeks following ovariectomy in the femur, in each study. The loss o f trabecular BMD depended on slice location, and varied from 0 to 22% at 6 weeks, and from 0 to 26% at 14 weeks (P < 0.001, at the affected locations). The antiresorptive effect of treatment was demonstrated in the 6-week study: there was no significant difference in BMD between sham-operated and E2-treated OVX rats.