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Bone Density or DEXA Scanning

Osteoporosis is a condition where the bones lose density - they become 'thinner' - which makes them more likely to break. People taking steroids have an increased chance of developing osteoporosis. If you are likely to be taking steroids by mouth for some time, or have other conditions making osteoporosis more likely, your GP or consultant may arrange for the density of your bones to be measured with a special (DEXA) scan. Repeat scans may be performed, generally every one or two years, to monitor the state of your bones.

You may have to ask your doctor to arrange bone density scanning for you. In our experience it does not necessarily happen automatically.

What is a Bone Density Scan (DEXA)?

A Bone Density Scan is a form of X-ray that is used to measure the density of bones. Dual energy X-ray absorptiometry (DEXA) scanning has become the most widely used method for measuring bone mineral density because it is quick, easy, reliable and uses very little irradiation. DEXA scanning is most often performed on the lower spine and hips.

What Happens when you have a DEXA Scan?

Inform your doctor if you have recently had a barium examination or have been injected with contrast material for any other X-ray. If you have had these, you may have to wait 10 to 14 days before undergoing a DEXA scan. Women should always inform their doctor or X-ray technician (radiographer) if there is any possibility that they are pregnant.

You should wear loose, comfortable clothing, with no metal such as zippers, belts or buckles. You will need to remove all items from your pockets for the scan.

A DEXA scan is performed as an outpatient procedure. You will be asked to lie on an examination table for a short time while the arm of the scanning machine passes over your body taking measurements. It is important that you stay as still as possible during the procedure to ensure a clear, useful image.

The DEXA scan is usually completed within 5 to 20 minutes, depending on the equipment used and the parts of the body being examined. The test is painless, there is no discomfort and no injections are involved. You will not be placed in a tunnel and so will not feel enclosed. The technician will remain with you throughout the scan.

How does a DEXA Scan work?

It works by using two X-ray beams of different energies. These are absorbed in different ways by the body’s tissues and, from this, the machine can calculate the density of your bones.

Who interprets the results and how will I get them?

A radiologist (a doctor specifically trained to supervise and interpret X-rays), will analyse the images and send a report to your GP or referring doctor, who will discuss the results with you.

Your test result is generally given in the form of a T score which compares the density of your bones with that of healthy young adults. If your T score is greater than -1.0 your bone density is said to be normal. If your T score is between -1.0 and -2.5 then you are said to suffer from osteopenia. If your T score is less than -2.5 you are said to have osteoporosis.

Less often you might see the term Z score which is a comparison of your bone density with that of other people of your age. A particularly low Z score might alert the doctor to perform further tests.

Osteopenia is really very common and affects about one in six young people, and more as we get older. It does not mean that you are unwell. If your scan results show that you have osteopenia, your GP will usually suggest some life style changes such as including more calcium in your diet, stopping smoking, cutting down on alcohol intake and taking regular weight bearing exercise such as brisk walking or running. If you are not already on Vitamin D your GP may also advise you to take this as it helps calcium to be absorbed into the body. Unless you are taking steroids, you will not normally be prescribed any additional medication if you have osteopenia. You can increase your bone density by following the life style changes suggested.

If your scan shows you have osteoporosis, your GP or referring doctor will discuss options with you.

This leaflet has been written by patient, Rea Mattocks, and has been checked for medical accuracy by Dr J Armitstead Associate Specialist, St Mary's Hospital, London. Published November 2009.
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