Dual Energy X-ray Absorptiometry
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Dual Energy X-ray Absorptiometry

(Bone Mineral Density Testing; DEXA; DXA)

En Español (Spanish Version)

Definition

DEXA is a dual energy x-ray absorptiometry test measures the density (or thickness) of your bones.

Parts of the Body Involved

The DEXA scan takes measurements at the spine, hip, and wrist, and sometimes other sites, such as a finger or the heel bone. Measurements of the spine and hip are called central DXA. Those done at the arms or legs are called peripheral DXA. In some cases, your doctor may order a whole body scan.

Reasons for Procedure

This 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.

Osteoporosis

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Risk Factors for Complications During the Procedure

No complications are expected from this procedure.

What to Expect

Prior to Procedure

Eat normally on the day of the exam, but do not take 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 Procedure

You will lie, fully clothed, on a cushioned table. You will stay motionless while the arm of the DEXA machine passes over your body taking measurements.

Anesthesia

No anesthesia is required. This procedure is painless.

Description of the Procedure

Total Body Measurement

As you lie on the table, the machine passes over your body and takes measurements of your bone density by sending a thin, invisible beam of low-dose x-rays through your bones. The amount of radiation is very small, less than 1/10 the dose of a standard chest x-ray . Based on how much the x-rays have changed after passing through your bones, a picture of your skeleton will be generated.

Spine or Hip Measurement

Your toes are placed in a “pigeon-toed” position, and the same procedure as above is followed.

Wrist Measurement

You sit in a chair beside the DEXA machine, and your arm is placed in a holding device while the measurement is taken.

After Procedure

After the procedure you will return home.

How Long Will It Take?

The scan takes approximately ten minutes to complete.

Will It Hurt?

This procedure is completely noninvasive and painless.

Possible Complications

There are usually no complications from this procedure. There is a small amount of radiation exposure, less than 1/10 the dose of a standard chest x-ray. Radiation exposure is cumulative over a lifetime.

Average Hospital Stay

You will not be admitted to the hospital for a DEXA scan. It is an outpatient procedure.

Postoperative Care

No special postprocedure care is required.

Outcome

The 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.

These test results will help your doctor to determine your risk for bone fractures. The lower your bone density, the higher your risk for bone fracture will be.

Call Your Doctor If Any of the Following Occurs

Call your doctor if you have any questions about the procedure, your condition, or your test results.

RESOURCES:

The American Academy of Orthopaedic Surgeons
http://www.aaos.org

National Osteoporosis Foundation
http://www.nof.org

References:

Sartoris D, Dalinka MK, Alazraki N. Osteoporosis and bone mass measurement. Radiology. 2000;215(suppl):397-414.

Osteoporosis: bone density tests. Am Acad Orthop Surg Bull . 1999;47(3).

National Osteoporosis Foundation website. Available at: http://www.nof.org/ . Accessed October 14, 2005.



Last reviewed November 2007 by Rosalyn Carson-DeWitt, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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