Rapid small-animal dual-energy X-ray absorptiometry using digital radiography.
Although dual-energy X-ray absorptiometry (DEXA) is an established technique 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 implemented a clinical digital radiography system to perform rapid area DEXA analysis on in vitro rat bone specimens. A crossed step-wedge (comprised of epoxy-based materials that mimic the radiographic properties of tissue and bone) was used to calibrate the system. Digital radiographs of bone specimens (pelvis, spine, femur, and tibia from sham-ovariectomized [SHAM] and ovariectomized [OVX] rats) were obtained at 40 kilovolt peak (kVp) and 125 kVp, and the resulting areal BMD values were compared with those obtained with a clinical fan-beam DEXA system (Hologics QDR 4500). Our investigation indicates that the cross-wedge calibrated (CWC) DEXA technique provides high-precision 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 by the CWC-DEXA system are within 8.5% of those reported by a clinical fan-beam scanner, and BMC values are within 5% of the known value of test specimens. In an in vivo application, the CWC-DEXA system is capable of reporting significant differences between study groups (SHAM and OVX) that are not reported by a clinical fan-beam DEXA system, because of the reduced variance and improved object segmentation provided by the CWC-DEXA system.
Holdsworth
D W
DW
Imaging Research Laboratories, John P. Robarts Research Institute, London, Ontario, Canada.
Thornton
M M
MM
Drost
D
D
Watson
P H
PH
Fraher
L J
LJ
Hodsman
A B
AB
D015502:Absorptiometry, Photon / Q000295:instrumentation* / Q000379:methods*; D000818:Animals; D015519:Bone Density; D001842:Bone and Bones / Q000000981:diagnostic imaging*; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging; D066298:In Vitro Techniques; D010052:Ovariectomy; D010388:Pelvis / Q000000981:diagnostic imaging; D011856:Radiographic Image Enhancement; D051381:Rats; D017207:Rats, Sprague-Dawley; D013131:Spine / Q000000981:diagnostic imaging; D013977:Tibia / Q000000981:diagnostic imaging