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Osteoporosis Health Center

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DEXA Scan (Dual X-ray Absorptiometry) to Measure Bone Health

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How is bone mineral density measured?

Dual X-ray absorptiometry (DXA) is the preferred technique for measuring bone mineral density (BMD). DXA has also been called dual energy X-ray absorptiometry, or DEXA. DXA is relatively easy to perform and the amount of radiation exposure is low. A DXA scanner is a machine that produces two X-ray beams, each with different energy levels. One beam is high energy while the other is low energy. The amount of X-rays that pass through the bone is measured for each beam. This will vary depending on the thickness of the bone. Based on the difference between the two beams, the bone density can be measured.

At present, DXA scanning focuses on two main areas -- the hip and spine. In certain situations -- if the hip or spine can't be measured, for instance -- it is measured in the forearm. Although osteoporosis involves the whole body, measurements of BMD at one site can be predictive of fractures at other sites. Scanning generally takes 10 to 20 minutes to complete and is painless and noninvasive.

Recommended Related to Osteoporosis

Osteoporosis Medications: How They Work

Think your bones stopped growing by the time you finished high school? Think again. Bones constantly remodel themselves throughout life, growing here, thinning there. In osteoporosis, though, normal bone remodeling goes awry. Bone loss exceeds bone growth, and bones become thin and weak. Osteoporosis affects 10 million Americans, leading to 1.5 million fractures every year. Osteoporosis medications and physical activity can tip the balance of bone remodeling, preserving bone strength. How...

Read the Osteoporosis Medications: How They Work article > >

WebMD Medical Reference

Reviewed by David T. Derrer, MD on January 23, 2016
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