DEXA (Bone Densitometry)
What is DEXA?
To accurately detect osteoporosis, doctors commonly use DEXA (which stands for the imposing term Dual-Energy X-ray Absorptiometry) bone densitometry to measure bone mineral density (BMD). DEXA is a quick, painless procedure for measuring bone calcium loss. Measurement of the lower spine and hips are performed.
What are some common uses of this procedure?
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.
DEXA is also effective in tracking the effects of treatment for osteoporosis and other conditions that cause bone loss.
The DEXA test can also assess an individual’s risk for developing fractures.
Bone Densitometry testing is strongly recommended if you:
- Are a post-menopausal woman and not taking estrogen.
- 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 and certain barbiturates, or high-dose thyroid replacement drugs.
- Have type 1 diabetes (formerly called juvenile or insulin-dependent), liver disease, kidney disease or a family history of osteoporosis.
- Have high bone turnover, which shows up in the form of excessive collagen in urine samples.
- Have a thyroid condition, such as hyperthyroidism.
- Have a parathyroid condition, such as hyperparathyroidism.
- Have experienced a fracture after only mild trauma.
- Have had x-ray evidence of vertebral fracture or other signs of osteoporosis.
The Lateral Vertebral Assessment (LVA), a low-dose x-ray examination of the spine to screen for vertebral fractures that is performed on the DEXA machine, may be recommended for older patients, especially if:
- They have lost more than an inch of height.
- Have unexplained back pain.
- If a DEXA scan gives borderline readings.
How should I prepare for this procedure?
- Refrain from taking calcium supplements for at least 24 hours beforehand.
- Wear comfortable clothing and avoid garments that have zippers, belts or buttons made of metal.
- Let your technologist know if you’ve recently had a barium examination or have been injected with a contrast material for a CT or radioisotope scan.
- Let your technologist know if there is a possibility you are pregnant.
What can I expect during this exam?
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 tube below and a detector (an imaging device) above. It is important that you remain as still as possible during the procedure to ensure a clear and useful image.
- Bone loss in the spine and hip are where most osteoporosis-related fractures happen:
- During an examination of the spine, your legs will be supported on a padded box to flatten your pelvis and lower (lumbar) spine.
- During examination of the hip, the technologist will place your foot in a brace that rotates the hip inward.
- The detector is scanned over the area, generating images on a computer monitor.