Academic and pharmaceutical researchers commonly use the mouse for investigations of genetics, cellular physiology, and of agents affecting bone or soft-tissue composition. Bone and tissue composition measurement using dual-energy x-ray absorptiometry (DEXA) densitometry eliminate the need for destructive chemical analysis - a time- and labor-consuming process that requires days or weeks to complete. DEXA densitometry allows the researcher the opportunity to make multiple measurements in situ during the life of the animal - providing true longitudinal measures. Unfortunately, the spatial resolution of table DEXA densitometers is too poor for mice and the rectilinear scanning process of older peripheral DEXA densitometers require as much as 30 minutes for a total body acquisition with relatively poor precision and spatial resolution. The long process requires careful sedation techniques and often endangers animal safety. The Lunar PIXImus Densitometer (GE Medical Systems) provides bone mineral and body composition results from total body imaging in less than 5 minutes. Fast imaging allows faster access to important data and is safer on animals.
The PIXImus allows automated, accurate and precise measurement of bone and tissue for small animals 10-50 g (e.g., mice, lemmings). These bone, fat and lean measurements exhibit excellent correlation to total their ashed or chemical extraction weights (r=0.99, 0.93, 0.99 respectively). PIXImus uses a lower x-ray energy than that used for peripheral densitometry in humans in order to achieve contrast in the extremely low density bone. Excellent precision of BMD and %Fat makes PIXImus ideal for longitudinal studies.
With an image area of 80 mm x 65 mm, the PIXImus can image the entire body of most mice and the subcranial region of large ob\ob mice. The standard total body result focuses on the sub-cranial region improving sensitivity by excluding the inactive bone and tissue of the cranium. There are manual regions of interest (ROIs) for selected areas within the total body image, such as spine and femur. Researchers using the rat can image large portions of the animal and position ROIs over their area of interest (i.e. entire leg, spine, abdomen…) producing both bone and tissue results.
PIXImus is driven by single-key commands and a graphical user interface. A single function key performs an automated image acquisition and analysis. Subject results are printed in a clear, easy-to-understand format, and data are stored electronically in a globally accepted format.
Save Animals - A 10-week 'longitudinal' study of body composition - with weekly data points and a sample size of 10 - require 100 animals (10 sacrificed per week for 10 weeks). While the PIXImus only needs 10 animals to be imaged weekly, in true longitudinal fashion, saving 90 animals.
1 Nagy TR, Clair AL Precision and Accuracy of Dual-Energy X-ray Absorptiometry for Determining in Vivo Body Composition of Mice Obesity Research 2000; Vol. 8 No. 5: 392-398
PIXImus's ultra-fast measurements and simple operation make it ideal for small animal research densitometry.