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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