Dual-energy X-ray absorptiometry

Dual-energy X-ray absorptiometry (also known as DXA, DEXA, or DXA scan) is a means of measuring bone mineral density (BMD). Two X-ray beams, with different energy levels, are aimed at the patient's bones. When soft tissue absorption is subtracted out, the BMD can be determined from the absorption of each beam by bone. Dual-energy X-ray absorptiometry is the most widely used and most thoroughly studied bone density measurement technology.

History

The DXA scan is typically used to diagnose and follow osteoporosis, as contrasted to the nuclear bone scan, which is sensitive to certain metabolic diseases of bones in which bones are attempting to heal from infections, fractures, or tumors.

Procedure

In a DXA scan, the patient lies on a padded table and an X-ray generator is located below. An imaging device, or detector, is passed over the patient, generating images on a computer monitor.

Applications

DXA scans are also used to measure total body composition and fat content with a high degree of accuracy comparable to other accepted methods such as underwater weighing and multi-compartment models. They can also be used to estimate visceral fat by subtracting subcutaneous fat within an anatomical landmark region.

Risks

As a radiation-based method, DXA scanning is not completely without risks, though the radiation dose is considered minimal.

See also

• Bone density
• Osteoporosis
• Radiation

References

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Dual-energy X-ray absorptiometry

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  DEXA scanner in use
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  Bone densitometry scan illustration
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  DXA scan of Morbus Fabry
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  Dual-energy X-ray absorptiometry
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  DXA fat shadow