What Is Bone Densitometry?

Bone Densitometry, or DEXA, is a bone density test that determines if you have osteoporosis—a disease that causes bones to become fragile and more likely to break.

In the past, osteoporosis could be detected only after a bone break.  By that time, however, your bones could be irreversibly weak.  Bone densitometry makes it possible to know your risk of breaking and identifies those high-risk patients that may benefit from prevention medications, supplements and exercise.

Bone densitometry uses X-rays to measure how many milligrams of calcium and other bone minerals are packed into a segment of bone.  The bones that are most commonly tested are located in the lumbar spine, hip and forearm.  The test result is reported as a "T-score" that compares the 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 and bones have weakened so much that the chance of fracture, even with minimal trauma, is significantly increased.  It is normal to gradually lose bone strength after age 30, and unfortunately, osteoporosis is 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 debilitating fracture.  These antiresorptive medications can slow down or stop bone loss.  The likelihood of osteoporosis occurring in the future can even be predicted by noting the presence of lower-than-average bone mineral density, a condition called "osteopenia."  With early treatment, osteoporosis can usually be prevented.

How Is Bone Densitometry Performed?

normal osteoporosis

Patients lie on their back on a comfortable table while low-dose X-rays are used to analyze the mineral content of spine, hip or forearm 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.


HOLOGIC QDR 4500 SL ELITE SYSTEM–Utilized for early detection of osteoporosis. Reports include bone mineral density, future fracture risk calculations and recommendations for candidates at high risk.