Dual Energy X-ray Absorptiometry (DXA) is a diagnostic tool that allows physicians to measure bone mineral density (BMD) or bone mass.  DXA is considered a safe radiology procedure that uses a very small amount of x-ray to measure the amount of mineral in the bone.  The information that is gathered is calculated by a computer and compared to that of a group of “normal young adults” and to “people of your own age group.”  The difference in your results and the other two groups is given as your “scores.”  Along with other factors, this information assists your physician in determining if you have osteoporosis or are at risk to develop an osteoporosis-related fracture (your chances of breaking a bone from osteoporosis).  DXA is most often performed on the lower spine and hips. Currently, DXA is considered the most accurate method of detecting early signs of osteoporosis.

What is Osteoporosis

Osteoporosis is a condition that weakens the bones of your skeleton causing them to become fragile and more likely to break. Bones, like other tissues in your body, are living structures that constantly are changing. New bone is made and old bone is taken away. Osteoporosis develops when the pace of new bone formation cannot keep up with the loss of bone. If not prevented or if left untreated, osteoporosis can progress painlessly until a bone breaks. These broken bones, also known as fractures, occur typically in the hip, spine, and wrist.

Of notable concern are vertebral (spinal) and hip fractures. Vertebral fractures can result in serious consequences, including loss of height, intense back pain and deformity. A hip fracture often requires surgery and may result in loss of independent living.

Factors that increase risk of osteoporosis

• Age
• Female Gender
• Caucasian or Asian Descent
• Thin or Small Build
• Previous Fracture
• Family History of Osteoporosis
• Early Menopause
• Smoking
• Inactive Lifestyle
• Certain Medications (including steroids & thyroid hormones)
• Alcohol Abuse
• Inadequate Calcium Intake

 Facts about osteoporosis

• A silent, complex disease that increases bone loss and makes bone thin and brittle
• A preventable and treatable disease through early diagnosis
• Responsible for over two million fractures annually
• Affects forty-four million Americans, mostly women
• As many as one in two women and one in four men over the age of fifty will have an osteoporosis-related fracture in their lifetime

Preparation for the examination

There is no special preparation for the examination except to wear loose comfortable clothing without metal snaps or zippers.  If necessary, you will be asked to change into scrubs or a patient gown.  You may also be asked to remove jewelry, eye glasses and any metal objects or clothing that might interfere with the x-ray images.  Lockers are available to store your personal items while you have your examination however, it is recommended that you leave your valuable items at home.

If you recently had a barium examination or have been injected with a contrast material for a computed tomography (CT) scan or radioisotope scan you may have to wait 10 to 14 days before undergoing a DXA test.

Women should always inform their physician or x-ray technologist if there is any possibility that they are pregnant. Because x-rays are used to measure the amount of mineral in the bones during a DXA examination, these tests are not performed during pregnancy because radiation can be harmful to the fetus.

During the examination

You will lie on a comfortable, padded table.  Measurements of your spine and hips will be performed. The DXA equipment used at our facilities measures both hips at the same time improving diagnostic accuracy. A small “arm” of the equipment will move above you, over the area being examined, while the x-ray picture is taken.  During this time you must hold very still and may be asked to keep from breathing for a few seconds to reduce the possibility of a blurred image.

Results of the examination

A board certified physician will analyze the images and measurement scores and send a signed report to your primary care or referring physician, who will share the results with you.  Your test results will be in the form of two scores:

T score — 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, the first stage of bone loss. A score below -2.5 is defined as osteoporosis. The T score is used to estimate your risk of developing a fracture.

Z score — This number reflects the amount of bone you have compared with other people in your age group and of the same size and gender. If this score is unusually high or low, it may indicate a need for further medical tests.