Understanding Bone Densitometry
Bone densitometry, also called a bone mineral density (BMD) test or dual-energy x-ray absorptiometry (DXA), is an enhanced x-ray technology that uses low doses of radiation to measure bone loss and to predict your risk of bone fractures. People with osteoporosis—a condition in which deficiencies in calcium cause bones to become thinner, more fragile and prone to breaking—are most at risk of bone fractures.
Several different types of machines can perform bone densitometry, but the most common method is the DexaScan, which uses low doses of x-rays. Typically, these machines are used to scan the lower spine and hip regions, but smaller machines can measure the bone density in your wrist, fingers, leg or heel.
Because the machines give off such low doses of radiation, most experts consider the risk low, especially when compared with the benefits of early identification of osteoporosis.
Your Wellstar physician may recommend bone densitometry f you are a woman over the age of 65, a man over the age of 70, or have a series of risk factors associated with osteoporosis. These factors may include:
- Bone fracture after the age of 50 or a series of fractures after age 40
- Early menopause
- Family history of osteoporosis or hip fractures, especially in your parents
- Low body weight or above average height
- Use of certain medications that can cause bone loss, including corticosteroids such as Prednisone®, various anti-seizure medications such as Dilantin® or some barbiturates
- Rheumatoid arthritis, chronic kidney disease, eating disorders, Type 1 diabetes or liver disease
- Long-term smoking or drinking
A radiologist will supervise and interpret the bone densitometry, which provides two scores:
- T-score compares the amount of bone you have with that of a young adult of the same gender with peak bone mass. A score above -1 is considered normal. A score between -1 and -2.5 indicates the beginning of bone loss (osteopenia). A score below -2.5 is defined as osteoporosis.
- Z-score compares your bone density with that of other people your age, gender and race. Scores exceptionally high or low may indicate a need for further medical attention.
Before the procedure
Bone densitometry requires almost no preparation on your part. You should not take calcium supplements for at least 24 hours before your exam. On the day of the examination, you may eat normally. You should wear loose, comfortable clothing and avoid garments that have zippers, clasps, belts or any other metal fasteners. You will likely be asked to remove any jewelry, wallets, or anything that might interfere with the x-rays.
You should inform your radiologist or another Wellstar physician if you believe you might be pregnant or if you recently had a barium examination or a contrast material injection for a computed tomography (CT) scan or a nuclear medicine bone scan.
During the procedure
Bone densitometry is fast, easy and painless. When you arrive at the Wellstar Imaging Center, you will be asked to fill out a medical history form and listen to a brief explanation of the procedure.
For the examination, you lie on a padded table with an x-ray generator located at the base of the table and an imaging device or detector above the table. This overhead "arm" scanner will be positioned above you but will not touch you. You should remain still as it passes over you. The entire outpatient procedure takes about 15 minutes.
After the procedure
Once you have completed bone densitometry, you may resume your normal, everyday activities.
Resources & Support
Wellstar offers bone densitometry through the DexaScan procedure. Screenings are available at Wellstar Cobb Women’s Center, Wellstar Douglas Hospital, Kennestone Women's Imaging Center, Wellstar Kennestone Imaging Center in East Cobb, Wellstar Kennestone Imaging Center at Towne Lake, Wellstar Paulding Hospital and Wellstar Windy Hill Hospital.