The use of dual-energy x-ray absorptiometry in animals.

The use of dual-energy absorptiometry (DXA) to measure bone mineral content (BMC) and bone mineral density (BMD) is widespread in humans and has been adapted to animals because of the need to examine bone and body composition in longitudinal studies. In this review, the indications and techniques for DXA in small-sized animals (rodents, cats, and rabbits) and large-sized animals (dogs, swine, nonhuman primates, sheep, and horses) are discussed. Now that software has been developed for measuring BMD in small laboratory animals, the most frequent use of DXA in animals is in rats. An ultrahigh-resolution mode of acquisition is used for their small bones but also is necessary for other small-sized animals such as rabbits and cats. In larger-sized animals such as dogs, pigs, and sheep, software used in humans has been adapted successfully to measure BMC/BMD and body composition. The human spine and left and right hip protocols are adapted easily to animals of this size, and the software for body composition has been adapted to dogs. Measurement of bone mass around metallic implants is possible in animals and most studies have involved dogs. To ensure precision of DXA in the noninvasive measurement of BMD in animals, attention to positioning and ability of the operator to define the same region of interest using clearly defined anatomical landmarks on the scan image cannot be overemphasized. This is one of the essential requirements for successful densitometry in animals.