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HARDWARE INFORMATION

Dual Energy X-ray Absorptiometry (DXA, previously DEXA)
Hardware Type
Imaging Systems

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Description
Dual Energy X-ray Absorptiometry (DXA, previously DEXA) is a noninvasive technique that employs low dose radiation to measure bone, fat and lean tissue composition. DXA is used in clinical applications to determine bone mineral content in the skeletal system, particularly the lumbar spine and hips.

A DXA unit consists of a whole-body scanner frame, an x-ray source and detector, and a control computer. The subject is positioned on top of the scanner frame, in a supine position. The scanner moves above and below the subject, along the scanner frame.

The method is based on measurements of the attenuation coefficients of different radiation energies through a medium consisting primarily of two materials, bone and soft tissue. The dual energy method employs both high and low energy x-ray beams. By comparing the absorption of the low and high energy x-rays, the contribution of soft tissue can be identified, and eliminated for bone measurements. This allows for accurate measurements of bone mineral content (BMC) and bone mineral density (BMD) even in areas where the amount of soft tissue can be large and variable, such as the hip or spine.

Versions of this Hardware
+ Version Used During Space Shuttle Missions
+ Version Used During the NASA-Mir Missions
+ Version Used During the International Space Station (ISS) Experiments
+ Version Used During NASA Extreme Environment Mission Operations (NEEMO)
+ Version Used During Ground-based Experiments