What is DEXA?

DEXA stands for "dual energy x-ray absorptiometry." It is the most widely used technique for measuring bone mineral density (BMD) and diagnosing the presence of osteoporosis. This measurement is accomplished by computer analysis of the difference in absorption of x-ray beams of two differing energies that have been passed through the spine and hips. (The spine and hips are examined because bones in these areas bear a great deal of stress, and because fractures in the spine and hip are among the most disabling when they occur.) The test result is reported as a "T-score" - which compares a patient's bone mineral density to that of a healthy young person.

Osteoporosis is defined by the World Health Organization as abnormally low bone mineral density (BMD), with a T-score of -2.5 or less. This means that bone mineral density has dropped to a dangerous level, when bone have weakened so much that the chance of a fracture occurring, even with minimal trauma, is significantly increased. It is normal to gradually lose bone strength after the age of 30, and osteoporosis is unfortunately very common in older individuals, especially women.

Bone densitometry is usually indicated for women who are over age 65, are considering starting or stopping hormone replacement therapy, or are menopausal/perimenopausal with any risk factors.

There are several medications that can effectively treat osteoporosis, and reduce the chance of a debilitating fracture. The likelihood of osteoporosis occurring in the future can even be predicted by noting the presence of a lower-than-average bone mineral density, a condition called "Osteopenia." By beginning early treatment, osteoporosis can usually be prevented.

What to expect

You will be asked to lie on your back on a comfortable table while low-dose x-rays are used to analyze the mineral content of both your spine and hip bones. The exam takes about 15 minutes and is completely painless. The amount of x-ray used is extremely small - equivalent to about 1/10 the dose received from a chest x-ray.