A DEXA scan is a dual-energy X-ray method that measures your bone mineral density and bone loss. It’s used to calculate osteoporosis and fracture risk.
A DEXA scan is a high-precision type of X-ray that measures your bone mineral density and bone loss. If your bone density is lower than normal for your age, it indicates a risk for osteoporosis and bone fractures.
“DEXA” stands for “dual-energy X-ray absorptiometry.” This technique was introduced for commercial use in 1987. It involves sending two X-ray beams at different peak energy frequencies to the target bones.
One peak is absorbed by soft tissue and the other by bone. When the soft tissue absorption amount is subtracted from the total absorption, the remainder is your bone mineral density.
The test is noninvasive, fast, and more accurate than a regular X-ray. It involves an extremely low level of radiation.
The World Health Organization (WHO) established DEXA as the best technique for assessing bone mineral density in women in postmenopause. DEXA is also known as DXA or bone densitometry.
The cost of a DEXA scan varies based on where you live and the type of facility performing the test.
Insurance companies usually cover all or part of the cost if your doctor says the scan is medically necessary. If you have insurance, you might need to pay a copay.
The out-of-pocket cost of a DEXA scan may be anywhere from $160 to $1,130 or more. It’s best to check with the facility and, if possible, to shop around.
Medicare
Medicare Part B fully covers a DEXA test once every 2 years, or more often if it’s medically necessary and you meet at least one of these criteria:
- Your doctor determines that you’re at risk for osteoporosis, based on your medical history.
- X-rays show the possibility of osteoporosis, osteopenia, or fractures.
- You’re taking a steroid drug such as prednisone.
- You have primary hyperparathyroidism.
- Your doctor wants to monitor to see whether your osteoporosis drug is working.
A DEXA scan is used to determine your risk of osteoporosis and bone fracture. It may also be used to monitor whether your osteoporosis treatment is working. Usually, the scan will target your lower spine and hips.
Standard X-ray diagnostics used before the development of DEXA technology could not detect bone loss until someone had lost
Before DEXA, a broken bone might be the first sign of bone density loss in an older adult.
When your doctor will order DEXA
Your doctor may order a DEXA scan if you:
- are a woman age 65 years or older or a man age 70 years or older (the recommendation of the National Osteoporosis Foundation and other medical groups)
- have symptoms of osteoporosis
- break a bone after 50 years of age
- are a man 50 to 59 years old and have risk factors
- are a woman in postmenopause, are under 65 years old, and have risk factors
Osteoporosis risk factors include:
- use of tobacco and alcohol
- use of corticosteroids and some other drugs
- low body mass index (BMI)
- some diseases, such as rheumatoid arthritis
- physical inactivity
- family history of osteoporosis
- previous fractures
- height loss of more than an inch
Measuring body composition
Another use for DEXA scans is to measure body composition, lean muscle, and fat tissue. DEXA is much more accurate than the traditional BMI in determining excess fat. A total-body picture can be used to assess weight loss or muscle strengthening.
DEXA scans are usually outpatient procedures. No special preparations are needed, except to stop taking any calcium supplements for 24 hours before the test.
Wear comfortable clothing. Depending on the body area being scanned, you may have to take off any clothes that have metal fasteners, zippers, or hooks. The technician may ask you to remove any jewelry or other items that may contain metal, such as keys. You may be given a hospital gown to wear during the exam.
Let your doctor know in advance if you’ve had a CT scan that required the use of contrast material or if you’ve had a barium exam. They may ask you to wait a few days before scheduling a DEXA scan.
You should also let your doctor know if you’re pregnant or suspect you might be pregnant. They may want to take special precautions or postpone the DEXA scan until after you deliver your baby.
The DEXA apparatus includes a flat padded table that you lie on. A movable arm above holds the X-ray detector. A device that produces X-rays is below the table.
The technician will position you on the table. They may place a wedge under your knees to help flatten your spine for the image or to position your hip. They may also position your arm for scanning.
The technician will ask you to hold very still while the imaging arm above slowly moves across your body. The X-ray radiation level is low enough to allow the technician to stay in the room with you while operating the device.
The whole process takes just a few minutes.
A radiologist will read your DEXA results and give them to you and your doctor in a few days.
The scoring system for the scan measures your bone loss against that of a healthy young adult, according to standards established by the WHO. This is called your T-score. It’s the standard deviation between your measured bone loss and the average.
- A score of -1 or above is considered normal.
- A score of -1.1 through -2.4 indicates osteopenia, an increased risk for fracture.
- A score of -2.5 or below indicates osteoporosis, a high risk for fracture.
Your results may also include a Z-score, which compares your bone loss to that of others in your age group.
The T-score is a measurement of relative risk, not a prediction that you’ll have a fracture.
Your doctor will go over the test results with you. They’ll discuss whether treatment is necessary and go over your treatment options. They may want to follow up with a second DEXA scan in 2 years to measure any changes.
If your results indicate osteopenia or osteoporosis, your doctor will discuss with you what you can do to slow down bone loss and stay healthy.
Treatment may simply involve lifestyle changes. Your doctor may advise you to start engaging in weight bearing exercises, balance exercises, or strengthening exercises, or they may recommend a weight loss program.
If your vitamin D or calcium level is low, they may recommend that you start taking supplements.
If your osteoporosis is more severe, your doctor may advise that you take one of the many medications that are designed to strengthen bones and reduce bone loss. Be sure to ask about the side effects of any medications.
Making a lifestyle change or starting a medication to help slow your bone loss is a good investment in your health and longevity. Studies suggest that 50% of women and 25% of men over 50 years old will break a bone because of osteoporosis, according to the Bone Health & Osteoporosis Foundation (BHOF).
It’s also helpful to stay informed about new studies and possible new treatments. If you’re interested in talking with other people who have osteoporosis, the BHOF has support groups around the country.