Bone density tests provide information about the health status of your bones. Normal bone is dense and strong, while bone in patients with osteoporosis is thinner, porous and more likely to break. A bone density exam compares your test results with the average bone mass of healthy adults, as well as to adults of your same age and ethnicity. Following your bone loss over time allows your doctor to determine if it is decreasing at an abnormally rate that might indicate osteoporosis. If that is the case, treatment can be started.
Bone density is affected by heredity, diet, sex hormones, physical activity, lifestyle choices and the use of certain medications. By age thirty, your bones have reached their highest density and will begin to gradually weaken, or lose density. This loss is very gradual for women until menopause when it then accelerates. One third of the total lifetime bone loss can occur in the first five years after menopause. Thus, bone density tests are performed most frequently in women age 65 and older. Women with a family history of osteoporosis or who start menopause at an early age should be tested younger. Men can also develop the disease and therefore, should be tested.
Bone densitometry can be performed with machines that measure density in the hip, spine and total body and peripherally in the fingers, wrists, kneecaps, shins and heels. The test uses a small amount of radiation (about one tenth the dosage of a chest x-ray). Most commonly, a Dual Energy X-ray Absorptiometer (DEXA) scanner is used to measure the spine, hip or total body. In other instances, bone densitometry of the spine can be performed with a computerized tomography scanner (CT scan). Certain devices that measure bone density in the wrist or foot use sound energy (ultrasound) to determine bone density.