Bone density scanning, also called dual-energy x-ray absorptiometry (DEXA) or bone densitometry, is an enhanced form of x-ray technology that is used to measure bone loss. DEXA is today’s established standard for measuring bone mineral density.
DEXA 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, as well as structural changes, that causes bones to become thinner, more fragile and more likely to break.
Preparing for your DEXA test
What to eat: On the day of the exam you may eat normally. However, you should not take calcium supplements for at least 24 hours before your exam.
What to wear: You should wear loose, comfortable clothing, avoiding garments that have zippers, belts or buttons made of metal. Objects such as keys or wallets that would be in the area being scanned should be removed.
You may be asked to remove some or all of your clothes and to wear a gown during the exam. You may also be asked to remove jewelry, dentures, eye glasses and any metal objects or clothing that might interfere with the x-ray images.
Prior exams: Inform your physician if you recently had a barium examination or have been injected with a contract material for a computed tomography (CT) scan or radioisotope scan. You may have to wait 10 to 14 days before undergoing a DXA test.
Pregnancy: You should inform your physician and x-ray technologist if there is any possibility that you are pregnant. Many imaging tests are not performed during pregnancy so as not to expose the fetus to any radiation. If an x-ray is necessary, precautions will be taken to minimize radiation exposure to the fetus.
HOW DOES A DEXA TEST WORK?
A DEXA scan works by measuring the amount of x-rays that are absorbed by your bones. Two types of x-rays are emitted by the DEXA scanner – one type absorbed by soft tissue and the other by bone – and are used to accurately calculate your bone density.
IS A DEXA TEST SAFE?
DEXA scans have been used safely for many years to calculate bone density. The amount of radiation absorbed through a DEXA test is substantially lower than that of a traditional x-ray of the chest.
WHAT SHOULD I EXPECT WHEN I ARRIVE?
When you arrive, you will be greeted by our staff who will direct you to complete any necessary paperwork. One of our friendly staff members will then guide you to the examination room.
HOW IS THE PROCEDURE PERFORMED?
This examination is usually done on an outpatient basis.
If you are having a Central DEXA examination, which measures bone density in the hip and spine, you will lie on a padded table with an x-ray generator located below and an imaging device, or detector, positioned above.
If you are having a spinal assessment, your legs will be supported on a padded box to flatten the pelvis and lower (lumbar) spine. To assess the hip, your foot will be placed in a brace that rotates the hip inward. In both cases, the detector is slowly passed over the area, generating images on a computer monitor.
To ensure the clearest image possible, you should hold very still and may be asked to hold your breath for a few seconds while the x-ray image is taken.
HOW LONG WILL MY DEXA TEST TAKE?
The DEXA bone density test is usually completed within 10 to 30 minutes, depending on the part(s) of the body being examined.