Bone density changes gradually over time, and those changes may not be visible from the outside. A DEXA scan is one of the most widely used imaging tests for measuring bone mineral density. Understanding how the scan works, as well as why a provider may order it, can help patients approach the process with clarity.
What Is a DEXA Scan?
DEXA stands for dual-energy X-ray absorptiometry; some providers also refer to it as a DXA scan or a bone densitometry test. The scan uses two X-ray beams set at different energy levels. Bone and soft tissue absorb these beams in different amounts, which allows the equipment to separate the two and calculate the mineral content of the bone being measured.
The amount of radiation used during a DEXA scan is low. The equipment differs from a standard X-ray machine, such as in its design and its purpose. A traditional X-ray produces an image that shows the shape and structure of bones; a DEXA scan produces numerical data that describes how dense the bone is in specific areas. Many scans focus on the lower spine and the hip.
What Is It Used For?
Health care providers use DEXA scans for several purposes, but the most common is measuring bone mineral density. This measurement can help a physician evaluate whether a patient’s bones are within an expected range or whether they show signs of thinning. A provider may recommend a DEXA scan for a variety of reasons, including:
- Age-related Screening: Medical guidelines often suggest bone density testing for women and men once they reach certain ages.
- Personal or Family History: A history of fractures, or a family history of bone conditions, may prompt a provider to request testing.
- Existing Health Conditions: Some hormonal conditions can affect how the body maintains bone.
- Monitoring Over Time: Patients who are already under care for low bone density may undergo repeat scans so their providers are able to track changes.
The results of a DEXA scan are one part of a broader evaluation. A physician typically reviews the findings alongside a patient’s medical history, lifestyle factors, and other test results before discussing any next steps.
What Should You Expect?
Preparing for a DEXA scan is straightforward. Many facilities will ask you to stop taking calcium supplements at least 24 hours before your appointment. You’ll also want to wear clothing without metal parts, but you may be asked to change into a gown regardless. If you’ve recently had a barium study or received contrast material for another test, let the facility know ahead of time.
During the appointment, you’ll lie on a table while the technologist positions you for each measurement. For a spine scan, your legs may be placed on a block to help flatten the lower back; for a hip scan, a brace is used to rotate your foot slightly inward. Both adjustments are simple.
A mechanical arm then passes slowly over the body while the equipment collects data. The process involves no needles or injections, and the machine does not enclose the body. The entire appointment usually takes between 10 and 30 minutes, depending on how many areas are scanned. After the scan, most patients may resume their normal activities right away.
Confer With an Imaging Expert
DEXA results are useful when they can be compared accurately over time. For this reason, follow-up scans may be performed on the same machine or the same type of equipment used for the original test. An imaging specialist is able to explain how the scan is performed, and they can describe the information the report contains.
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