Bone densitometry evaluates bone density by examining the bone mineral content in the hip, spine and forearm. Bone densitometry is a simple and painless procedure that uses a low dose X-ray to detect signs of bone thinning and mineral loss.
About bone densitometry
- Detects early stages of osteoporosis.
- Tracks the effects of treatment for osteoporosis and other conditions that cause bone loss.
- Rates bone health using scores that compare the patient's bones with those of other healthy people of the same age group, size and gender.
What can a bone densitometry scan tell my doctor?
Bone densitometry is especially helpful in detecting the early stages of osteoporosis, before symptoms occur. Osteoporosis is a condition that affects mostly post-menopausal women over the age of 65. However, men can be afflicted as well.
While everyone loses bone mass with age, osteoporosis increases the risk for fractures. These fractures most commonly occur in the hips and vertebrae. The good news is, with bone density testing, most of these patients can be treated before bones lose too much strength.
Bone density testing is recommended for:
- Women past menopause.
- Patients age 65 and older.
- Patients who use medications known to cause bone loss, including corticosteroids such as prednisone, some anti-seizure medications, some barbiturates, or high-dose thyroid replacement drugs.
- Patients with type 1 diabetes, liver disease, kidney disease or a family history of osteoporosis.
- Patients who have high bone turnover, the process of breaking down and reforming bone.
- Patients with a thyroid condition.
- Cases of fracture after only mild trauma.
- Evidence of vertebral fracture in an X-ray.
How do I prepare for my exam?
A bone density scan requires little preparation.
- Wear loose, comfortable clothing with no metal zippers or buttons. Other items, such as jewelry or any other metal objects, may need to be removed before the exam so that they do not interfere with the X-ray.
- Do not take any calcium supplements, vitamin pills or mineral supplements 24 hours prior to your appointment.
- Do not take any medications for osteoporosis or osteopenia for 24 hours prior to your appointment.
- Other than those exclusions, you may eat normally and take medications as prescribed by your doctor the morning of your test.
In addition, you must not have had any exams involving barium or radioisotopes within the last two weeks.
How is the test performed?
Depending on what type of machine is used, you may be asked to either lie down on a table or put your foot in a special device.
If your doctor wants to measure bone density in your hip and spine, you will lie on a padded table. An X-ray generator will be located under the table and an imaging device above.
Special software will be used to evaluate your spine, and you will be asked to lie comfortably on the table.
To look at the hip, your feet will be rotated inward utilizing a special positioning device that will rotate the hips inward.
When the X-ray passes over, you must be still for a few seconds to prevent movement. This will help create a sharper image that's not blurred.
A bone density test can take up to 30 minutes.
Are there risks?
Bone densitometry tests are very safe. However, the machines that use X-rays should not be used on pregnant women. This is usually not a problem since osteoporosis usually happens during and after menopause.
What do my results mean?
Your doctor will use a scale to rate your bone scan.
T score — The T score is used to estimate your risk of developing a fracture.
This number shows the amount of bone you have compared with 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 is classified as osteopenia (low bone mass). A score below -2.5 is defined as osteoporosis.
Z score — This number looks at the amount of bone you have compared with other people in the same age group and of the same size and gender. If the score is unusually high or low, further medical tests may be required.
How will I receive the results?
The information from the scan is processed by a computer and interpreted by a radiologist, endocrinologist, or rheumatologist. The results are based on an international scoring system, explained above. A final report will be sent to your referring physician to review with you.