Dual Energy X-Ray Absorptiometry (DEXA) Scan Definition

A dual energy x-ray absorptiometry (DEXA) scan, also called bone densitometry, is a medical imaging technique that measures the density of bones. Compared to a regular x-ray scan, a DEXA scan is much more sensitive to changes in bone density. As relates to the spine, this scan is commonly used to assess the risk for osteoporosis and vertebral fractures.

How a DEXA Scan Works

A DEXA machine consists of a table and a scanning arm. To measure bone density:

  • The patient lies still on his/her back on the table.
  • The scanning arm moves slowly, typically emitting 2 beams of low-dose x-rays into the lower spine, hip, and/or wrist.
  • Images of the scanned areas are produced on a computer screen.

The amount of x-ray absorbed by the bones is then calculated.

When a DEXA Scan Is Considered

A DEXA scan is useful in assessing:

  • The risk of developing osteoporosis, a condition in which bone density decreases, resulting in fragile and brittle bones
  • Bones that may be susceptible to fracture
  • The progress of osteoporosis treatment

A DEXA scan is a relatively safe procedure, but there are some cases when it is not recommended. For example, women who are pregnant are advised to avoid a DEXA scan due to the radiation exposure.

A DEXA scan may also be used to measure the body’s muscle and fat content. In such cases, the entire body is scanned and the amount of x-ray absorption in the soft tissues is calculated.

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