Women's Imaging

What is Bone Mineral Densitometry?

Every day, 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 a quick, painless procedure for measuring bone loss and is the established standard for measuring bone mineral density (BMD). Measurement of the lower spine and hips is most commonly performed, but examination of the wrist, fingers and heel may also be utilized.

What are some common uses of the procedure?

DEXA bone densitometry is used to diagnose osteoporosis, a condition that typically affects women after menopause, but may also be found in premenopusal women and men. Osteoporosis involves a gradual loss of bone, causing them to become thinner, more fragile, and more likely to break. The DEXA test can 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 these treatments for osteoporosis or for other conditions that cause bone loss.

Bone density testing is strongly recommended if you:

• Are a peri- or post-menopausal woman
• Have a personal or maternal history of hip fracture or 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 corticosteroids such as Prednisone, various anti-seizure medications such as Dilantin, certain barbiturates, 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 high bone turnover, which shows up in the form of excessive collagen in urine samples
• 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 should I expect during the procedure?

During the procedure you will lie supine on a cushioned table and a low dose X-ray beam will pass over your body, measuring the density of your lower spine, hip and in some cases, wrist. You should remove all metal objects during the exam including zippers, belts and coins. If you have had a recent barium exam or a nuclear medicine procedure where radioactive material has been administered, you may have to postpone the examination until the barium and radioactivity have cleared form your system.

What do the results mean?

Your bone density will be reported as a T-score and a Z-score. The T score compares your bone density, in standard deviations above or below that of a young adult of the same sex with peak bone mass. A score above -1 is considered normal. A score between -1 and -2.5 is classified as osteopenia, or mild bone loss. A score below -2.5 is defined as osteoporosis.

The Z score compares your bone density to other people of the same sex in your age group. It is also reported in standard deviations above or below the bone density of age matched controls.

Based on these results, your physician will determine if further tests and/or osteoporosis therapy are indicated. Your test data is automatically stored at MDR for future comparison. Because bone density measurements may vary from manufacturer to manufacturer, and even from machine to machine, it is highly recommended that you return to MDR for your followup examinations for the most accurate assessment of change in bone density.