What Is Bone Densitometry (DEXA)?
A 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. A bone density test makes it possible to know your risk of breaking and identifies those high-risk patients that may benefit from prevention medications, supplements and exercise.
A bone density test uses X-rays to measure how many grams 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” – 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, and that bones 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/premenopausal 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.
How is Bone Densitometry Performed?
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 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.