Dual-energy X-ray absorptiometry (DEXA) is an imaging technology that uses a very low amount of X-ray energy to detect the presence of osteoporosis.
Osteoporosis is a disease that gradually weakens bones, leading to bone fragility and an increased chance of fractures to the spine, hips and wrists. This weakening may be due to aging or caused by other risk factors that combine with age.
Often called the "silent disease," osteoporosis rarely shows symptoms until a lot of bone mass has been lost. The most visible symptoms may include loss of height along with curvature of the upper back.
DEXA scanning can identify low bone density in patients at an early stage, enabling doctors to prescribe appropriate treatment before the condition worsens. Images of the lower spine and hips are most often used in checking for osteoporosis. The test results are then read thoroughly and interpreted by radiologists, who sub-specialize in musculoskeletal radiology.
Who Needs a DEXA Bone Density Scan?
While the disease affects both men and women, 80% of those affected are women. In fact, 22 million American women are affected by osteoporosis.
Women have a higher risk for osteoporosis than men because women often have smaller, thinner frames. In addition, menopause causes women to produce less estrogen, a hormone that helps protect them against bone loss; 20% of bone mass can be lost in the 5-7 years following menopause.
If you're nearing menopause, your doctor or healthcare professional can give you good advice to help you avoid future problems with osteoporosis. If you are post-menopausal, stay in touch with your doctor to monitor your bone health on a regular basis. If you don't know if you have osteoporosis, ask whether a bone density test is right for you. Your doctor will need to refer you for this exam.
For your convenience, bone density exams can be scheduled along with your mammogram appointment.
- Factors that may add to the risk of osteoporosis include:
- Caucasian or Asian
- Advanced age
- History of bone fracture
- Small, thin frame
- Family history of osteoporosis
- Post menopause, including early or surgically induced
- Low calcium diet
- Lack of exercise
- Eating disorders
- Abnormal absence of menstrual periods
- Certain medicines (such as steroids and anticonvulsants)
- Alcohol or tobacco use
How to Interpret DEXA Scan Results
The test compares your bone mineral density (BMD) to that of a "young adult" at peak bone strength and to people of your same age, called "age-matched". The difference between your result and that of a "young adult" is given as a T-score.
This information, along with other factors, helps doctors in making a diagnosis. The following T-scores define the amount of bone loss:
- Normal: T-score above -1
- Osteopenic (low bone density): T-score between -1 and -2.5
- Osteoporosis: T-score below -2.5
Your test results combined with other factors give you and your doctor an overall risk of fracture. Knowing your risk of a fracture is important, because there are many ways to prevent osteoporosis and to reduce fracture risks.
After reviewing your DEXA scan results your doctor may suggest a number of steps important in building bone strength.
Suggestions may include:
- Changes in diet
- Hormone therapy
- Medicines known to improve bone strength