BONE DENSITOMETRY
A Patient's Guide to Understanding

What is osteoporosis and how is it diagnosed?

Osteoporosis, a disease that lowers bone density and causes brittle bones, affects over 25 million Americans. Annually, this disease is responsible for over 1.3 million fractures, of which 250,000 are hip fractures. Increased awareness of osteoporosis has led to more advanced methods of diagnosing and monitoring the disease. To assist in diagnosing low bone density, physicians may choose to prescribe an examination called bone densitometry, or bone density test.

The following are frequently asked questions about bone densitometry. If you have any additional questions or concerns, please contact your physician.

What causes osteoporosis?

Bone is living tissue that is constantly being broken down and reformed. As a person grows, bone forms faster than it breaks down until it reaches a peak bone mass between the ages of 25 and 35. After age 35, both men and women lose bone at a greater rate than it forms, causing bone loss. Women after menopause start to lose bone at a much more rapid rate than men of the same age. This rapid bone loss is usually due to the decrease in the production of the estrogen hormone. As a greater amount of the bone is lost, the bones become porous and brittle.

Why is bone density testing available?

Bone density tests are the most practical way to accurately measure the density of your bones. The examination estimates the amount of bone mineral content in specific areas of your body, including the spine, hip and forearm, and in the total body. A physician assesses the risk factors and will review the results of a Bone Mineral Density test. When bone density tests are repeated over time, they can help your doctor track your rate of bone loss.

How is the bone density test done?

You will be asked to lay perfectly still during the test. An arm will pass over the region of your body being measured. A dual-energy beam of x-ray passes through your body and is measured by a detector in the arm. This technology is called Dual-Energy X-ray Aborptiometry or DXA. The Excell(TM) bone densitometer works by measuring the amount of x-rays that are absorbed by the bones in your body. The two x-ray energies allow the machine to tell the difference between bone and soft tissue, giving a very accurate estimation of bone density.

Is a bone density test the same as a bone scan?

No. Often confused with a nuclear medicine bone scan, a bone density test is faster and does not require a radionuclide injection.

How long does the exam take?

Please allow 15 to 30 minutes for your scheduled appointment.

How much radiation is involved?

The amount of radiation from a typical bone density test is only a fraction of that received from a standard chest x-ray. Or, in other words, it is comparable to the amount received on a transcontinental airline flight. Patients should always inform the technologist if there is any chance of pregnancy.

Are there any special preparations required?

Unless instructed otherwise, you should eat normally on the day of the exam. You may prefer to call and inquire about specific instructions.