USDA/ARS Children's Nutrition Research Center

PIXImus

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Please read the PIXImus Request and Use Procedures for information about the access and use of this system.

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Capabilities

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PIXImus
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The PIXImus (General Electric) uses the principles of dual x-ray absorptiometry (DXA) to measure bone mineral density, lean and fat tissue masses for small animals that weigh less than approximately 75 g. Two X-ray beams, with different energy levels, are aimed at the mouse. When soft tissue absorption is subtracted out, the bone mineral density (BMD) can be determined from the absorption of each beam by bone. The PIXImus measurement requires that the animal is immobilized during the measurement. Mice must be sedated before and throughout the measurement.

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Measurement Procedure

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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 oriented carefully 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. If you prefer, you may use an injectable anesthetic. The mouse is inserted into the instrument for measurement (approx. 5 minutes) and then returned to a cage to recover under observation. Once fully recovered the mouse can be returned to its home cage. 

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 (see References). 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)