What is a bone density scan?
This test -- also called a DEXA scan -- is used to detect osteoporosis, a weakening of the bones that might lead to fractures of the spine, hip or wrist. A bone density measurement determines your bone mineral density (BMD) for the area measured and compares that result with the average BMD of young adults of your sex and race at their peak BMD.
This information will help your doctor determine if you need to take certain steps to protect your bone health. Early detection is the best way to protect yourself from the possible damaging effects of osteoporosis.
Bone density measurement is simple, safe, noninvasive and painless - you don't even need to undress for the procedure, which requires no special preparation, medication or injection.
What can I expect?
The bone densitometer is like a large, padded examination table. Your name, age, height, weight and ethnicity will be entered into the computer before your test. This information is used to compare your results to a normal reference group.
You will be asked to lie on your back, remaining in your normal clothing in most cases. Belt buckles, metal or thick plastic buttons and metal jewelry will need to be removed from the area being examined. The operatorwill position your arms and legs for the test, which is painless and typically takes less than 30 minutes. You should lie still and breathe normally. Do not take calcium pills the day of the test.
How will it feel?
A bone density test is safe and painless, though you will need to lie still while a scanner passes over your body.
How does the densitometer work?
A bone densitometer measures bone mineral density (BMD). The amount of bone mineral relates directly to bone density. The bone densitometer uses small amounts of x-ray to measure BMD and to produce images of the spine, hip, or even the whole body. The spine and hip are measured because that is where most osteoporotic fractures occur.
What information will the test give my doctor?
A bone densitometry test can help your doctor diagnose osteoporosis. The test compares your bone to that of a "young adult" at peak bone strength - this is called your T-score. The World Health Organization (WHO) has developed categories that define the amount of bone loss:
Normal: T-score above -1
Osteopenic (low bone mass): T-score between -1 and -2.5
Osteoporotic: T-score below -2.5
Your T-score combined with other risk factors will enable your doctor to estimate what your risk of a hip fracture or other major osteoporosis-related fracture will be in the next 10 years. This information will help your doctor determine what course of action should be taken.
The bone densitometry test is also useful in following bone changes. Your doctor may suggest follow-up tests to detect change over time.
Where can I get more information about bone measurements and osteoporosis?
The National Osteoporosis Foundation provides information about osteoporosis and bone measurements.