Bone Mineral Density
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Osteoporosis: Should I Have a Dual-Energy X-Ray Absorptiometry (DXA) Test?
Why It Is Done
A bone mineral density (BMD) test is
- All women who are age
65 or older, and younger women who are at increased risk for broken bones caused by osteoporosis.1
- Men with risk factors for
osteoporosis, such as being older than 70.
- Men and women who have
- Men and women who
have been taking
corticosteroids, such as prednisone, for a long
- Follow-up of how well treatment for osteoporosis is working
for men and women being treated for 2 years or longer.
How To Prepare
Avoid wearing clothes with metal buttons
or buckles for the test. You also may want to remove any jewelry that might
interfere with the scan, such as a bracelet if you are having the scan done on
How It Is Done
A bone mineral density (BMD) scan is usually
done in the special radiology department or clinic by a technologist.
Peripheral dual-energy X-ray absorptiometry (P-DEXA) machines are portable
units that can be used in a doctor's office.
You will need to lie
on your back on a padded table. You can usually leave your clothes on. You may
need to lie with your legs straight or with your lower legs resting on a
platform built into the table.
The machine will scan your bones
and measure the amount of radiation they absorb. The DEXA technique, which
scans the hip and lower spine, takes about 20 minutes to perform. Other
techniques may take 30 to 45 minutes.
Portable machines (P-DEXA)
can measure bone density in the wrist or forearm.
Testing at least two different bones
(preferably the hip and spine) each time is the most reliable way of measuring
BMD. It is best to test the same bones and to use the same measurement
technique and BMD equipment each time.
How It Feels
A bone mineral density test does not cause
pain. If you have back pain, it may be uncomfortable to lie still on a table
during the scan.
During a bone mineral density (BMD) scan, you are
exposed to a very low dose of radiation. A BMD scan is not recommended for
pregnant women because of the radiation exposure to the unborn baby.
A bone mineral density (BMD) test measures
the density of minerals (such as
calcium) in your bones using a special
computed tomography (CT) scan. Results are usually available in 2 to 3