RADIOLOGY/IMAGING
Bone Densitometry
A Bone Density Scan is a quick and painless
procedure. Bone density scanning, is also referred to as a
DEXA scan (dual-energy x-ray absorptiometry). It is an
enhanced form of x-ray technology used to measure bone loss.
The amount of radiation used is extremely small-less than one tenth
the dose of a standard chest x-ray.
How is it performed?
DEXA is most often performed on the lower spine and hips.
You will be asked to lie on a large, flat table while a mechanical
arm passes over your body. The DEXA machine sends a thin,
invisible beam of low-dose x-rays with two distinct energy peaks
through the bones being examined. One peak is absorbed mainly
by soft tissue and the other by bone. The soft tissue can be
subtracted from the total and what remains is a patient's bone
mineral density.
Why is it performed?
DEXA is most often used to diagnose osteoporosis, a condition
that affects women after menopause but may also be found in
men. Osteoporosis involves a gradual loss of calcium, as well
as structural changes, causing the bones to become thinner, more
fragile and more likely to break.
A bone density test tells you if you have normal bone density,
low bone density (osteopenia) or osteoporosis. It is the only
test that can diagnose osteoporosis. The lower your bone
density, the greater your risk of breaking a bone. A bone
density test can help you and your healthcare provider:
- Learn if you have weak bones or osteoporosis
before you break a bone
- Predict your chance of breaking a bone in the future
- See if your bone is improving, getting worse or staying the
same
- Find out how well an osteoporosis medicine is working
- Let you know if you have osteoporosis after
you break a bone
How do I prepare?
On the day of the exam you may eat normally. You should
not take calcium supplements for at least 24 hours before your
exam. You should wear loose, comfortable clothes with no zippers,
belts or metal buttons. You may be asked to change into a
hospital gown for your comfort. .
First, you will need to tell your doctor if:
- You might be pregnant
- Have recently had a radiology exam with barium
- Have recently had a computed tomography (CT) scan or
radioisotope scan with contrast material
You may have to wait 10 to 14 days before undergoing a Bone
Density Scan.
What should I expect?
When assessing the spine, your legs are supported on a padded
box to flatten the pelvis and lower spine. When assessing the
hips, your foot is placed in a race that rotates the hip
inward. In both cases, the detector is slowly passed over the
area, generating images on a computer monitor.
You must hold very still and asked to hold your breath for a few
seconds while the x-ray image is obtained to reduce the possibility
of a blurred image. The technologist will walk behind a wall
to activate the x-ray machine.
The test is usually completed within 10 to 30 minutes.
Who should have a bone density test?
The National Osteoporosis Foundation recommends that you have a
bone density test if:
- You are a woman age 65 or older
- You are a man age 70 or older
- You break a bone after age 50
- You are a woman of menopausal age with risk factors
- You are a postmenopausal woman under age 65 with risk
factors
- You are a man age 50-69 with risk factors
A bone density test may also be necessary if you have
any of the following:
- an X-ray of your spine showing a break or bone loss in your
spine
- back pain with a possible break in your spine
- height loss of ½ inch or more within one year
- total height loss of 11/2 inches from your original height