Bone Mineral Density Scan
(Bone Densitometry, BMD, Dual Energy X-ray Absorptiometry, DEXA Scan, Photon Absorptiometry)
BMD Overview
Making sure your bones stay strong is a common concern for men and women as we age. Bones naturally grow thinner as you grow older because existing bone breaks down faster than new bone is made. As this occurs, your bones lose calcium and become more fragile, leading to a condition called osteoporosis. If not prevented, or left untreated, osteoporosis can progress silently until a bone breaks (fractures). Any bone can be affected, but a hip or spinal fracture can cause prolonged or permanent disability, or even death.
CML HealthCare clinic, Bone Mineral Density scan.
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Description of the bone mineral density test
A bone mineral density (BMD) scan is a non-invasive, pain-free test that measures the thickness of your bones, examining whether your bones are weak (low density) or strong (high density) in order to determine your chances of developing osteoporosis later in life.
The higher the bone density, the better. To use a simple analogy, a dense bone would be like a giant straw filled with sand, with very small spaces between each grain of sand. A low density, or more fragile, porous bone on the other hand, would be like a giant straw filled with rocks, with large spaces between them.
Bone Mineral Density FAQs
Why is a bone mineral density test performed?
This test is used to both screen for osteoporosis and see how well osteoporosis treatments are working. It is also useful for people who:
- are over the age of 65,
- have had fractures of the spine,
- have an excessive curvature of the spine,
- are taking certain steroid medications (which can increase the risk of osteoporosis),
- have lost at least 4 cm in height (or at least 2 cm in the last year), and/or
- may be at risk of developing osteoporosis.
How often should a bone mineral density test be performed?
Your first bone density test tells you the current density of your bones at that specific time. However, it cannot tell you if you have lost bone or are currently losing bone. Your doctor will let you know how often you need this test to check for weak bones or to see how your osteoporosis treatments are working.
Are there any risks or precautions?
Although the test is very safe, it is not recommended for anyone who is pregnant or suspects that they may be pregnant. There are no side effects, and exposure to radiation during the test is minimal.
What happens during the bone mineral density test?
The bone mineral density test is non-invasive (meaning that nothing is inserted through your skin or into a body cavity) and pain-free. Areas tested may include the lower part of your spine (also called the lumbar region), the upper part of the thigh bone near the hip joint, the wrist, the forearm, the finger, or the heel.
For most bone mineral density tests, you lie on a table while an X-ray detector moves above your spine and hip. One or both sides of your body may be scanned while the detector measures the amount of radiation, in the form of X-rays, that is able to pass through your bone. The denser (stronger) your bones are, the less radiation will be able to pass through them.
How should I prepare for the bone mineral density test?
BMD tests require very little preparation. You only need to avoid wearing jewellery and having metal objects on your body or metal buttons on your clothing. You may need to wear a hospital gown. Tell your doctor or the person doing the test if you have had a bone fracture in the area being scanned (this can artificially increase your score, making your bones appear thicker than they are), or a test involving barium or dye injections in the last two weeks (this can interfere with the test).
Be sure to tell your doctor or pharmacist about all prescription, over-the-counter, non-prescription, and herbal medications that you are taking, and about any medication allergies and medical conditions that you may have. Also ask whether you need to stop taking any of your medications before the test.
What can I expect after the bone mineral density test?
You can return to your normal activities immediately after the test.
Bone Mineral Density Results
There are two scores used to interpret bone density test results: the T-score and the Z-score. The T-score compares your bone density to the average density of healthy young adults of your same gender who are at their highest lifetime bone mass.
If you have a high amount of bone loss, your doctor will tell you, in standard deviation units (SDs), how much below "normal" you are. If your bone density is more than 2.5 SDs below normal, you will be diagnosed with osteoporosis.
Click here for bone mineral density requisition forms
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