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The most common way to measure bone mass probably is a procedure known as dual X-ray absorptiometry (DXA). Doctors may measure only certain bones in the body, such as the pelvic and spinal bones, or they may measure bone mass in the entire skeleton. The procedure is considered very safe, even for children and infants. Experts believe that the DXA machine administers only about 10 percent of the radiation that patients typically receive during a chest X-ray.
The DXA procedure generally requires the patient to recline on a special table. The table emits X-rays, which pass upward through the patient's body. A second component of the DXA machine, which passes through the air over the patient's body, absorbs the X-rays. The machine can measure bone density by calculating the number of X-rays that pass through the body. Healthy, dense bones normally stop more X-rays from passing through the body.
Bone mass, also known as bone mineral density, refers to the strength and thickness of the skeletal bones. People with low bone density usually have thin, brittle bones that can fracture easily. High bone mass is usually associated with stronger, sturdier bones. A bone mineral density test can help doctors measure bone strength by measuring the density of bones. A bone mineral density test can be useful for diagnosing and monitoring the progression of bone diseases that cause abnormal bone mass, such as osteoporosis.
The DXA procedure is considered harmless and is usually painless. It can be used to diagnose bone mass problems in people of all ages, and is even used to monitor the progression of bone diseases in infants and young children. DXA can also diagnose osteoporosis, an age-related thinning of the bones that often strikes elderly women.
While routine bone density measurements aren't usually recommended for healthy children and adults, certain people may want to consider them. Physicians may recommend regular bone density measurements for people with certain bone diseases. While infants and children with bone disease may need frequent bone mass measurements, adults with bone disease usually only need them annually.
Regular bone density measurements are sometimes recommended for people who have not yet been diagnosed with a bone disease. Women over age 65 are considered at high risk for osteoporosis, and are usually advised to receive regular bone density measurements. Postmenopausal women who have suffered a bone fracture or who are considered high risk for osteoporosis may need to have regular bone mass density measurements. Some men may be at risk for osteoporosis, as well. Any adult who has used steroid drugs for longer than 90 days may also have suffered loss of bone density.