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This completely painless, non-invasive procedure will help your doctor assess the density of your bones, and determine if you have osteoporosis, a bone thinning disease. This information may be used to predict your risk of bone fractures. The lower your bone density, the higher your risk for bone fracture will be. Most physicians recommend that women have a baseline bone density test done at the time of peri-menopause or post-menopause, repeating every two years after menopause. The test may also be necessary for men at risk for osteoporosis, usually over age 65.
Also known as a Dual Energy X-ray Absorptiometry (DEXA) scan, this test scans your bones and measures the density (or thickness) of your
 spine and hip ("central DXA")
wrist and sometimes other sites,
such as a finger or the heel bone ("peripheral DXA")
In some cases, your doctor may order a whole body scan.
What to expect
Before the Exam: Avoid taking
calcium supplements for at least 24 hours prior to the exam. If you
have had a barium study, or have been injected with contrast dye
for a CT scan or MRI, wait at least seven days before undergoing
a DEXA scan. Wear loose, comfortable clothing. Avoid clothing with
metal zippers, belts, or buttons.
During the Procedure: During the scan, which takes approximately 10 minutes to complete, you will lie fully clothed on a cushioned table. You will remain still while the arm of the DEXA machine passes over and scans your body, measuring your bone density by sending a thin, invisible beam of low-dose x-rays (less than 1/10 the dose of a standard chest x-ray) through your body. Based on how much the x-rays have changed after passing through your bones, a picture of your skeleton will be generated.
After the Procedure: The most important part of any imaging test is the skill and experience of the expert who reads it. There are no experts with greater experience and knowledge than those at NewYork-Presbyterian Hospital. Test results are usually available within a few days. Your test results will show two types of scores:
T
score — this number shows the amount of bone you
have in comparison to a young adult of the same gender with
peak bone mass. A score above -1 is considered normal. A score
between -1 and -2.5 is classified as osteopenia, the first
stage of bone loss. A score below -2.5 is defined as osteoporosis.
Z
score — this number shows the amount of bone you
have in comparison to other people of your age group, gender,
and size.
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