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BONE DENSITY SCAN
Dual-energy x-ray absorptiometry (DXA) test measures the density
of minerals – such as calcium – in your bones using a
special X-ray. It is an
enhanced form of x-ray technology that is used to measure bone loss. DXA is today's established
standard for measuring bone mineral density (BMD).
A bone mineral density (BMD)test measures the density
of minerals – such as calcium – in your bones using a
special X-ray.
A DEXA bone density scan provides an
estimate of the strength of your bones. DEXA uses two
different X-ray beams to estimate bone density in your spine
and hip. The amounts of each X-ray beam that are blocked by
bone and soft tissue are compared to each other. Bones with
higher mineral density (BMD) allow less of the X-ray beam to
pass through them. DEXA is the most accurate method for
measuring BMD. DEXA can measure as little as 2 percent
of bone loss per year. It is fast and uses very low doses
of radiation.
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What to do prior to scheduling bone density scan?
On the day of the exam you may eat normally. You should not take calcium supplements for at least 24
hours before your exam.
You should wear loose, comfortable clothing, avoiding garments that have zippers, belts or buttons
made of metal. Objects such as keys or wallets that would be in the area being scanned should be
removed..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 your wrist.
Inform your physician if you recently had a barium examination or have been injected with a contrast
material for a computed tomography (CT) scan or radioisotope scan. You may have to wait 10 to 14
days before undergoing a DXA test.
Women should always inform their physician and x-ray technologist if there is any possibility that they
are pregnant. Many imaging tests are not performed during pregnancy so as not to expose the fetus to
radiation.
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Equipment and procedure
The DXA machine sends a thin, invisible beam of low-dose x-rays with two distinct energy peaks
through the bones being examined. One peak is absorbed mainly by soft tissue and the other by bone.
The soft tissue amount can be subtracted from the total and what remains is a patient's bone mineral
density.
DXA machines feature special software that compute and display the bone density measurements on a
computer monitor. You will lie on your back on a padded table.An x-ray generator is located below the patient and an imaging device, or detector, is
positioned above.
You can usually remain fully clothed. You may lie with your legs
straight or with your lower legs resting against a platform built
into the table. The machine will scan your bones and measure
the amount of radiation they absorb. Testing at least two
different bones each time – preferably the hip and spine – 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. The DEXA technique, which scans the hip
and lower spine, takes only about 20 minutes to perform.
Usually there is no discomfort during a bone mineral density
test. Bone density tests are a quick and painless procedure.
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What happens after the test?
| A radiologist will interpret
your exam. The technologists who administer the test cannot
interpret or discuss what they are viewing while performing
the exam. A report will be sent to your physician’s office to
discuss results.
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SERVICES
