A bone densitometry scan is a test that is carried out to measure the density of mineral in bone and to evaluate bone density loss. This test is used to diagnose osteoporosis, a bone condition that develops as a result of calcium loss in bones. Bone densitometry is also known as dual-energy X-ray absorptiometry or bone density scanning.
Osteoporosis is a degenerative bone disease that most commonly develops in postmenopausal women but also can develop in men. This bone disease develops when calcium and other minerals are absorbed from bones, often as a result of calcium deficiency. People with this disease have a greatly increased risk of bone fractures. Osteoporosis can be diagnosed with bone densitometry, and the test also can be used to evaluate bone fracture risk for someone with this disease.
A bone densitometry test involves the use of X-ray equipment capable of generating two X-ray beams instead of just one. Each beam emits X-rays of different energy levels, which allows bone density to be measured more accurately. The person undergoing the test lies down on an X-ray table during the test, and the X-ray beams measure the amount of energy that is absorbed by his or her bones. The amount of mineral present in bones affects the extent of X-ray energy absorption, so the information generated in the test can be used to determine the extent of bone loss in the person undergoing the test.
To determine whether an individual has osteoporosis, his or her bone density measurements are compared with a baseline measurement called peak bone mass. This measurement is defined as the average young adult bone density. A person is diagnosed with osteoporosis if his or her bone density measurement is at a certain level below the baseline. If the bone density measurement is between the baseline level and the level of osteoporosis diagnosis, the individual is diagnosed with osteopenia, or low bone mass. Someone who has osteopenia is at increased risk of osteoporosis.
Bone densitometry scanning is recommended for people who have an increased risk of osteoporosis and other degenerative bone diseases. Risk factors for osteoporosis include family history of osteoporosis; being a post-menopausal woman; smoking; type 1 diabetes; thyroid disease; and using corticosteroids, anti-seizure medications or barbiturates. For people with one or more risk factors, regular scans are a preventative measure to help people with osteoporosis or osteopenia reduce the risks of bone fracture.