Bone Density (DEXA)

Physicians use x-rays to view and evaluate bone fractures and other injuries of the musculoskeletal system. However, a plain x-ray is not the best way to assess bone density. To detect osteoporosis accurately, doctors use an enhanced form of x-ray technology called dual-energy x-ray absorptiometry (DXA or DEXA). DEXA bone densitometry is today's established standard for measuring bone mineral density (BMD).

DEXA is a quick, painless procedure for measuring bone loss. Measurement of the lower spine and hips are most often done. If you have had a hip replacement or have metal in your spine from back surgery, the forearm can be measured.

 

DEXA bone densitometry is most often used to diagnose osteoporosis, a condition that often affects women after menopause but may also be found in men. Osteoporosis involves a gradual loss of calcium, causing the bones to become thinner, more fragile, and more likely to break.

The DEXA test can also assess your risk for developing fractures. If your bone density is found to be low, you and your physician can work together on a treatment plan to help prevent fractures before they occur. DEXA is also effective in tracking the effects of treatment for osteoporosis or for other conditions that cause bone loss. Bone density testing is strongly recommended if you:

· are a post-menopausal woman and not taking estrogen

· have a personal history of smoking

· are a post-menopausal woman who is tall (over 5 feet 7 inches) or thin (less than 125 pounds)

· are a man with clinical conditions associated with bone loss

· use medications that are known to cause bone loss, including steroids, various anti-seizure medications, or high-dose thyroid replacement drugs

· have type 1 (formerly called juvenile or insulin-dependent) diabetes, liver disease, kidney disease, or a family history of osteoporosis

· have a thyroid condition, such as hyperthyroidism

· have experienced a fracture after only mild trauma

· have had x-ray evidence of vertebral fracture or other signs of osteoporosis

What to expect with your procedure

The DEXA bone density test takes 10 to 30 minutes, depending on the equipment used and the parts of the body being examined. You may be asked to undress and put on a hospital gown. Then you'll lie on a padded table with an x-ray generator below and a detector (an imaging device) above.

During an examination of the spine, your legs will be supported on a padded box to flatten your pelvis and lower (lumbar) spine. To assess your hip, the technologist will place your foot in a brace that rotates the hip inward. In both cases the detector is slowly passed over the area, generating images on a computer monitor.

Preparing for your procedure

On the day of the exam eat normally, but don't take calcium supplements for at least 24 hours beforehand. Wear loose, comfortable clothing, avoiding garments that have zippers, belts or buttons made of metal.

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 DEXA test.

Women should always inform their physician or x-ray technologist if there is a possibility they are pregnant.