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DEXA Bone Density Scanning
DEXA is today's established standard for measuring bone mineral density
Arthritis & Sports is the only orthopaedics practice in Northern Virginia to offer DEXA services to its patients
Now with the ability to perform both adult and pediatric scans!
What is a DEXA scan?
Bone density scanning, also called DEXA (short for dual-energy x-ray absorptiometry) or bone densitometry, is an enhanced form of x-ray technology that is used to measure bone loss and is today's established standard for measuring bone mineral density (BMD). By measuring the amount of bone in areas such as your hip and spine, the results of the DEXA scan can tell you if you have normal bone density, or if you have osteopenia or osteoporosis, and can determine your risk for fractures.
What are some common uses of the procedure?
DEXA is most often used to diagnose osteoporosis, a condition that often affects women after menopause but may also be found in men and rarely in children. Osteoporosis involves a gradual loss of calcium, as well as structural changes, 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. The risk of fracture is affected by age, body weight, history of prior fracture, family history of osteoporotic fractures, and lifestyle issues such as cigarette smoking and excessive alcohol consumption. These factors are taken into consideration when deciding if a patient needs therapy.
Who needs a DEXA scan?
People who should consider having a DEXA scan fall into four categories:
1. All women 65 years and older, and all men 70 years and older
2. Women under the age of 65 with any of the following risk factors:
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Estrogen deficiency
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History of amenorrhea before the age of 42, or early menopause
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Low body mass (less than 127 pounds)
3. Men and women of any age with any of the following risk factors:
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Family history of osteoporosis
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Vitamin D deficiency
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Loss of height
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Alcohol or cigarette use
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Prolonged immobilization
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Long term use of steroids
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Eating disorder, malnutrition or recent unexplained weight loss
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Broken bone from little or no trauma
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Hyperthyroidism or hyperparathyroidism
4. Children with any of the following risk factors:
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Recurrent fractures, bone pain, bone deformities, or osteopenia
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Low-impact fractures occurring from a standing height or less
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Cystic fibrosis and childhood cancer, including baseline levels by 18 years of age or 2 years after the end of chemotherapy (or earlier in patients with more severe disease, low body weight, chronic glucocorticoid therapy, delayed puberty, gonadal failure, or a history of fracture)
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Female adolescents with nutritional concerns, such as eating disorders and/or excessive exercise (scans recommended after 6 or more months of amenorrhea)
How should I prepare for the 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. 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, removable dental appliances, 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 DEXA test.
Women should always inform their physician and x-ray technologist if there is any possibility that they are pregnant. Many imaging tests are not performed during pregnancy so as not to expose the fetus to radiation. If an x-ray is necessary, precautions will be taken to minimize radiation exposure to the baby.
How is the DEXA scan performed?
The x-ray technician will help you lie on your back on a padded table. An x-ray generator is located below this table, with the imaging device attached to it. The scanner, which is positioned above you, will move back and forth as it measures your bone density or body composition. The machine is very open and does not feel “closed in” (see above photo).
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.
You will be asked to hold 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.
The DEXA 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. DEXA machines feature special software that computes and displays the bone density measurements on a computer monitor.
Is a DEXA scan safe?
A DEXA scan uses an extremely low dose of radiation and is considered safe for patients of any age. Radiation exposure from DEXA is less than one-tenth the dose of a standard chest x-ray and is comparable to being in the sun for 2-3 hours. The benefits of an accurate diagnosis far outweigh the risks of exposure.