bone densitometry (DEXA)
Bone densitometry or DEXA scans (short for dual-energy X-ray absorptiometry) identify a decrease in bone density and a loss of bone strength. DEXA scans determine the risk of fractures (broken bones) and can confirm a diagnosis of osteoporosis (or osteopenia). DEXA scans can provide physicians with an early diagnostic tool by which to determine whether osteoporosis treatment is needed.
Who should get a Bone Density scan?
- Women age 65 and older, men age 70 and older
- Postmenopausal women under the age of 65 with one or more risk factors
- Family history of osteoporosis (mother or sister)
- History of cigarette smoking, excessive alcohol or caffeine consumption
- History of diabetes, hyperparathyroidism, or hyperthyroidism
- Premature menopause or late onset of menstrual periods
- Vitamin D deficiency
- Long term use of medications known to cause bone loss (i.e., prednisone, seizure medications, diuretics and Depo-Provera contraceptive injections).
What to Expect
During a comprehensive examination with DEXA, you will lie comfortably still on a padded table while the DEXA unit scans two or more areas, usually the hip and spine. Unlike typical X-ray machines, radiation exposure during bone densitometry is extremely low, less than the radiation exposure during a coast-to-coast airline flight. The entire process takes only minutes to complete, depending on the number of sites scanned. It involves no injections or invasive procedures, and you may remain fully clothed.
Preparing for Bone Densitometry
Unless instructed otherwise, eat normally on the day of the exam, but avoid taking calcium supplements for at least 24 hours prior to your appointment. Wear loose, comfortable clothing. Sweat suits and other casual attire without zippers, buttons, grommets or any metal are preferred. You should not have had a barium study, radioisotope injection, oral or intravenous contrast material from a CT scan or MRI within seven days prior to your DEXA scan.
In certain patients, quantitative computed tomography (QCT) may be more sensitive than DEXA. Contact your physician if you have any of the following conditions to determine if QCT is a better alternative for you: severe aortic calcifications, degenerative spine changes, scoliosis, prior kyphoplasty, lumbar hardware, IVC filter, bone lesions, or morbid obesity (to 450#).
Similar to household scales, each DEXA machine has different calibration and sometimes different physics. Patients benefit from follow-up on the same unit.