What is a DEXA scan?
In a DEXA (dual energy X-ray absorptiometry) scan, a person lies on a table while a technician aims a scanner mounted on a long arm. Bone density scanning, also called dual-energy x-ray absorptiometry (DXA) or bone densitometry, is an enhanced form of x-ray technology that is used to measure bone loss. DXA is today's established standard for measuring bone mineral density (BMD).
How does it work?
The DEXA scanner uses beams of very low-energy radiation to determine the density of the bone. The amount of radiation is tiny: about one-tenth of a chest X-ray. The DXA machine sends a thin, invisible beam of low-dose x-rays with two distinct energy peaks through the bones being examined. One peak is absorbed mainly by soft tissue and the other by bone. The soft tissue amount can be subtracted from the total and what remains is a patient's bone mineral density. DXA machines feature special software that compute and display the bone density measurements on a computer monitor.
Pregnancy Test Required for Females-(waiver currently being used)
(Pregnancy test must be done within 48 hours of the test-Currently a waiver is in process for the Greatest Loser Contest-you must sign that you are not pregnant before the scan)
Females need to be cleared before testing by having a pregnancy test administered by a certified medical professional either at their local doctor’s office or school health clinic. Pregnant women should not get DEXA scans because the developing baby should not be exposed to radiation, no matter how low the dose, if possible.
How should I prepare for my DEXA scan?
On the day of the exam you may eat normally. You should not take calcium supplements for at least 24 hours before your exam. You should wear loose, comfortable clothing, avoiding garments that have zippers, belts or buttons made of metal. No metal can be worn when completing DEXA scan. Remember to empty out your pockets. Objects such as keys or wallets that would be in the area being scanned should be removed. You may also be asked to remove jewelry, removable dental appliances, glasses and any metal objects or clothing as these might interfere with the x-ray images and alter the final results for the testing.
What will I experience during and after my DEXA scan?
Bone density tests are a quick and painless procedure. Routine evaluations every two years may be needed to see a significant change in bone mineral density, decrease or increase. Few patients, such as patients on high dose steroid medication, may need follow-up at six months.
"DEXA currently is the easiest, most standardized form of bone density testing, so that's what we use," says Mary Rhee, MD, MS, an endocrinologist and assistant professor of medicine at Emory University in Atlanta.
While all of these can determine bone density and osteoporosis risk, "DEXA is the most important test and is the gold standard," says Felicia Cosman, MD, clinical director for the National Osteoporosis Foundation.