Bone Densitometry (DXA Scanning)
Bone densitometry is a type of imaging examination that measures your bone
mineral density, which is a sign of bone strength. Bones that are not very dense
become brittle and weak and are more likely to break. A number of conditions
cause a loss of bone mass, such as osteoporosis, some inherited diseases or
treatments for chronic diseases. Because postmenopausal women are at higher risk
for osteoporosis, the National Osteoporosis Foundation recommends that women
older than 65 undergo a bone densitometry test every 2 years.
Several imaging techniques may be used to measure bone density, including
ultrasound and computed tomography, but the most common method is dual-energy
x-ray absorptiometry, or DXA. DXA, pronounced “dexa,” uses x-rays to analyze the
amount of bone your skeleton has.
During a DXA scan, density measurements are taken of bones at specific areas
of your body. Those measurements then are compared to a database of “normal”
individuals of your same age, sex and race. The results show whether you have
lost bone density. The measurements also help determine the presence of
osteoporosis and can be used to estimate your risk of bone fracture. If you are
being treated for bone loss, a follow-up DXA scan can show if the therapy is
Before your examination, a radiographer will
explain the procedure to you and answer any questions you might have. A
radiographer, also known as a radiologic technologist, is a skilled medical
professional who has received specialized education in the areas of radiation
protection, patient care, radiation exposure, radiographic positioning and
The radiographer will ask you several questions about your medical history.
It is helpful to have a list of current medications and dosages you are taking.
The radiographer also may ask you if you are on hormone replacement therapy or
you have had recent medical imaging examinations such as an upper GI series.
Usually, you will be allowed to remain in your street clothes during the
examination, although some facilities may require you to put on a hospital gown.
Avoid wearing clothing with metal zippers, buckles, buttons or other metallic
objects because they may affect the bone density measurement. It is a good idea
to wear a comfortable, two-piece outfit such as a sweat suit since for many
measurements you will be lying on your back on an examination table.
During the Examination
The radiologic technologist
will position you on a padded table and ask you to remain as still as possible
during the test. The technologist then will use the DXA equipment to scan one or
more areas of bone — usually the lower back, hip, wrist or forearm. The DXA exam
does not hurt, and you will not feel anything when the x-rays pass through your
body. The exam takes about 15 to 20 minutes.
The DXA scanner computes a numerical reading of bone strength, called a T-score,
that is used to compare your bone density with established values.
Your physician will receive a report of the DXA findings. He or she then will advise you of the results and
discuss what further procedures, if any are needed. If you have low bone
density, you may be advised to take calcium supplements or other medication.
Your physician also may recommend that you participate in some kind of
weight-bearing exercise, such as walking, to strengthen your bones.
The above patient information provided by the American Society of Radiologic
Technologist (ASRT) with permission. www.asrt.org