Rapid small-animal dual-energy X-ray absorptiometry using digital radiography

Although dual-energy X-ray absorptiometry (DEXA) is an established techniqu e for clinical assessment of areal bone mineral density (BMD), the spatial resolution, signal-to-noise ratio, scan time, and availability of clinical DEXA systems may be limiting factors for small-animal investigations using a large number of specimens. To avoid these limitations, we have implemente d a clinical digital radiography system to perform rapid area DEXA analysis on in vitro rat bone specimens. A crossed step-wedge (comprised of epoxy-b ased materials that mimic the radiographic properties of tissue and bone) w as used to calibrate the system, Digital radiographs of bone specimens (pel vis, spine, femur, and tibia from sham-ovariectomized [SHAM] and ovariectom ized [OVX] rats) were obtained at 40 kilovolt peak (kVp) and 125 kVp, and t he resulting areal BMD values were compared with those obtained with a clin ical fan-beam DEXA system (Hologics QDR 4500), Our investigation indicates that the cross-wedge calibrated (CWC) DEXA technique provides high-precisio n measurements of bone mineral content (BMC; CV = 0.6%) and BMD (CV = 0.8%) within a short acquisition time (<30 s), Areal BMD measurements reported b y the CWC-DEXA system are within 8.5% of those reported by a clinical fan-b eam scanner, and BMC values are within 5% of the known value of test specim ens. In an in vivo application, the CWC-DEXA system is capable of reporting significant differences between study groups (SHAM and OVX) that are not r eported by a clinical fan-beam DEXA system, because of the reduced variance and improved object segmentation provided by the CWC-DEXA system.