Every day,physicians use radiography,or x-rays, to view and evaluate bone fractures and other injuries of the musculoskeletal system. However, a plain x-ray test 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. More portable devices that measure the wrist, fingers or heel are sometimes used for screening, including some that use ultrasound waves rather than x-rays.
DEXA bone density testing is the most accurate method available for the diagnosis of osteoporosis. It is also considered an accurate estimator of fracture risk. It will not tell whether you will or will not have a fracture, but gives relative risk of suffering a fracture, just as cholesterol and blood pressure help determine risk for heart disease. A low reading should not cause you to be anxious, but may help you set healthy goals. As with other diseases and conditions, early detection is the key to prevention of further bone loss and eventual fractures. DEXA equipment is widely available, making DEXA bone densitometry testing convenient for patients and doctors alike.
Frequently Asked Questions
- How should I prepare for the 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 10-14 days before undergoing a DEXA test. Women should always inform their physician or x-ray technologist if there is a possibility they are pregnant.
- What will I experience during the procedure??
DEXA bone densitometry is a simple, non-invasive procedure. Once on the table, you may be asked to hold an awkward position for a short time while the arm of the machine passes over your body taking measurements. It is important that you stay as still as possible during the procedure to ensure a clear, useful image. No anesthesia is required. The procedure is painless, and radiation exposure is minimal.
- What are the risks??
No complications are expected with the DEXA procedure.
- What are the limitations of DEXA Bone Densitometry??
Despite its effectiveness as a method of measuring bone density, DEXA is of limited use in people with a spinal deformity or those who have had previous spinal surgery. The presence of vertebral compression fractures or osteoarthritis may interfere with the accuracy of the test. CT scans may be more useful in such instances. DEXA cannot predict who will experience a fracture, but can provide indications of relative risk.Central DEXA devices are more sensitive than pDEXA devices, but they are also somewhat more expensive. The peripheral devices don’t accurately follow changes in your bones during therapy. A test done on a peripheral location, such as your heel or wrist, may help predict the risk of fracture in your spine or hip. But because bone mass tends to vary from one location to the other, measuring the heel is not as accurate as measuring the spine or hip.