Dexa Scan

What is Radiography-based (X-ray) Bone Densitometry?

To accurately detect osteoporosis, doctors commonly use DEXA bone densitometry to measure bone mineral density (BMD). DEXA (or DXA) is a quick, painless procedure for measuring bone loss. Measurement of the lower spine and hips are most often done. For measuring the wrist, fingers or the heel, more portable devices are sometimes used.

What are some common uses of this procedure?

DEXA bone densitometry is commonly 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 bones to thin, become more fragile, and more likely to break.

The DEXA test can also assess your risk for developing fractures and is effective in tracking the effects of treatment for osteoporosis and other conditions that can cause bone loss. Bone density testing is recommended for:

• post-menopausal women who are not taking estrogen.
• patients with a personal or maternal history of hip fracture or smoking.
• post-menopausal women who are tall (over 5 feet 7 inches) or thin (less than 125 pounds).
• men with clinical conditions associated with bone loss.
• patients who take medications that are known to cause bone loss.
• patients with type 1 diabetes, liver disease, kidney disease, or a family history of osteoporosis.
• patients with high bone turnover..
• patients with a thyroid condition, such as hyperthyroidism.
• patients who have experienced a fracture after only mild trauma.
• patients who had x-ray evidence of vertebral fracture or other signs of osteoporosis.

How should I prepare for this procedure?

• On the day of your exam, eat as you normally would.
• Don't take calcium supplements for at least 24 hours beforehand.
• Wear loose, comfortable clothing.
• Avoid garments that have zippers, belts, or buttons made of metal.
• Inform your doctor if you recently had a barium examination or have been injected with a contrast material for a CT or radioisotope scan.
• Women should inform their doctor or x-ray technologist if there is a possibility they are pregnant.

What can I expect during this procedure?

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

Most often, doctors focus on bone loss in the spine and hip where most osteoporosis-related fractures happen.

• Spine: During an examination of the spine, your legs will be supported on a padded box to flatten your pelvis and lower (lumbar) spine.
• 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.

Peripheral DEXA (pDEXA). You place your finger, hand, forearm or foot in a small device, and within a few minutes, a bone density reading is obtained.

What will I experience during this procedure?

DEXA bone densitometry is a simple, painless, and non-invasive procedure. Once on the examination table, you may be asked to stay still and to hold an awkward position for a short period of time while the machine takes measurements. It is important that you stay as still during the procedure to ensure a clear and useful image.

Who interprets the results and how do I get them?

The results of a DEXA bone density exam are interpreted by a radiologist and forwarded to your doctor. Your test results will be in the form of two scores:

T score: This number shows the amount of bone you have compared 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. It is used to estimate your risk of developing a fracture.

Z score: This number reflects the amount of bone you have compared to other people in your age group and of the same size and gender. If it is unusually high or low, it may indicate a need for further medical tests.