What is a Bone Density Scan (DXA)?
Bone density scanning, also called dual-energy x-ray absorptiometry (DXA) or bone densitometry, is a form of x-ray technology that is used to measure bone loss. DXA is today’s established standard for measuring bone mineral density (BMD). DXA is most often performed on the lower spine and hips.
What are some common uses of the procedure?
DXA bone densitometry is most often used to diagnose osteoporosis, a condition that often affects women after menopause. Osteoporosis involves a gradual loss of calcium, causing the bones to become thinner, more fragile and more likely to break.
DXA is also effective in tracking the effects of treatment for osteoporosis and other conditions that cause bone loss.
The DXA test can also assess an individual’s risk for developing fractures.
Bone density 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).
- 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 (formerly called juvenile or insulin-dependent) diabetes, liver disease, kidney disease or a family history of osteoporosis.
- 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.
Instant Vertebral Assessment (IVA), a low-dose x-ray examination of the spine to screen for vertebral fractures is also performed on the DXA machine.
How should I prepare for the procedure?
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.
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, eyeglasses and any metal objects or clothing that might interfere with the x-ray images.
Inform your physician if you recently had a barium examination or have been injected with a contrast material for a computed tomography (CT) scan or radioisotope scan. You may have to wait 10 to 14 days before undergoing a DXA test.
Women should always inform their physician or x-ray technologist if there is any possibility that they are pregnant.
What does the DXA equipment look like?
The device has a large, flat table and an “arm” suspended overhead.
How does the procedure work?
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.
How is the procedure performed?
This examination is usually done on an outpatient basis.
The patient lies on a padded table. An x-ray generator is located below the patient and an imaging device, or detector, is positioned above.
To assess the spine, the patient’s legs are supported on a padded box to flatten the pelvis and lower (lumbar) spine. To assess the hip, the patient’s foot is 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.
The patient must hold very still and may be asked to keep from breathing for a few seconds while the x-ray picture is taken to reduce the possibility of a blurred image.
An additional procedure called Instant Vertebral Assessment is also done. IVA is a low-dose x-ray examination of the spine to screen for vertebral fractures that is performed on the DXA machine.
The IVA test adds only a few minutes to the DXA procedure.
The DXA bone density test is usually completed within 10 to 30 minutes.
What will I experience during and after the x-ray procedure?
Bone density tests are a quick and painless procedure.
Who interprets the results and how do I get them?
A radiologist, a physician specifically trained to supervise and interpret radiology examinations, will analyze the images and send a signed report to your primary care or referring physician, who will share the results with you.
Your test results will include a T score:
This number shows the amount of bone you have compared with a young adult of the same gender with peak bone mass. A score above -1 is considered normal. A score between -1 and -2.5 is classified as osteopenia, the first stage of bone loss. A score below -2.5 is defined as osteoporosis. The T score is used to estimate your risk of developing a fracture.
Why Women’s Imaging Centre-Lafayette?
As a patient, you have a clear choice when it comes to medical imaging. At Women’s Imaging Centre-Lafayette, we make that decision easy by focusing on your total experience. We will make your imaging experience as convenient and comfortable as possible.
We offer:
- Easy scheduling and same day/next day appointments
- Comfortable surroundings
- Highly trained, caring staff
To schedule your appointment, please call (337) 993-8300