Mineral Density in Beagle Dogs: Comparison with Dual-energy X-ray

25 This study aimed to demonstrate the higher accuracy and reproducibility of quantitative 26 computed tomography (QCT) compared with dual-energy X-ray absorptiometry (DXA) as a gold 27 standard for measuring canine bone mineral density (BMD). Seven middle-aged beagle dogs 28 underwent lumbar vertebral and bilateral femoral DXA and QCT scans. BMD (mg/cm) was 29 measured at the vertebral body from L2 to L6, femoral neck, and proximal and distal femoral 30 diaphyses. The BMD values were measured 3 times and compared. The BMD value on QCT was 31 higher than that on DXA for femoral BMD but not for vertebral BMD. The correlation was 32 strong for the lumbar vertebrae (r = 0.66) and was strongest for L3 (r = 0.85). No correlation was 33 found for the femoral neck (P = 0.35), and only moderate correlations were found for the 34 proximal and distal femoral diaphyses (r = 0.43 and r = 0.40, respectively). The limits of 35 agreement were narrower for vertebral BMD than for femoral BMD, and L3 had the narrowest 36 limits of agreement. The intraclass correlation (ICC) was higher for DXA than for QCT at all 37 lumbar and femoral sites measured, but the ICC of QCT was higher than 0.7. In conclusion, L3 38 can be used to monitor changes in BMD, and relative values and sequential monitoring of 39 femoral BMD can also be useful because of the high reproducibility of QCT measurements. QCT 40 would be a useful technique for evaluation of BMD in veterinary practice. 41