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The PIXImus uses the principles of dual x-ray absorptiometry to measure bone mineral density, lean and fat tissue masses for small animals that weigh less than approximately 75 g. The PIXImus uses a lower x-ray energy than that used for peripheral densitometry in humans to achieve contrast in the extremely low density bone. Excellent precision of bone mineral density and body composition parameters makes PIXImus ideal for longitudinal studies. However, the PIXImus measurement requires that the animal is immobilized during the measurement. Mice must be sedated before and throughout the measurement.

There are some systematic errors in the lean and fat mass values obtained by PIXImus that vary depending on the instrument model and software version. To provide more accurate measurements, we have derived some correction equations to apply to the data generated by the CNRC PIXImus. The procedure and further information can be found below.

Download calculator for adjusting PIXImus body composition data to chemical analysis-comparable values (Microsoft Excel spreadsheet)


Body Composition Measurement


Total body fat, lean, and bone mineral content is measured by dual x-ray absorptiometry (DXA) using a PIXImus instrument (General Electric). The measurements are performed in a CNRF procedure room. Each mouse is lightly anesthetized by placing it in a chamber with isoflurane (5% and 95% oxygen). As soon as the mouse is sedated it is placed on a disposable PIXImus measuring tray for proper alignment and is fitted with a loosely-fitting nose cone for administration of isoflurane (2% isoflurane) until the measurement is complete. The mouse is inserted into the instrument for measurement (approx. 5 minutes) and then returned to its cage to recover. If you prefer, you may use an injectable anesthetic.