Bone densitometry

Femur, lumbar and whole body studies

The densitometry is an examination that uses low doses of X-ray, which pass through the entire body, for a radiography (not valid for radiodiagnostics), at the level of the lower backbone and hip. There are less sophisticated devices that can measure this density in the wrist and heal.

Therefore, through a low powered X-ray system, the bone mineral density can be measured, offering us data about the possible onset or presence of osteoporosis and the risk of bone fractures. In general, the density is measured according to the standards of age and each bone. This is why the density measurement in the wrist cannot provide data regarding the risk for hip fractures.

The densitometry is one of the most reliable techniques for measuring bone health so as to prescribe correct treatment for the prevention of osteoporosis.

Repeating the same technique allows for monitoring bone loss in individuals over time.

The densitometry also helps us control the improvement of bone density when a patient is undergoing treatment.

How the test is performed

During the main DEXA (dual energy X-ray absorptiometry) test, which measures bone density in the hip and backbone, the patient lies down on a cushioned table. An X-ray generator located under the patient and an imaging device, or detector, is placed over the patient.

To study the backbone, the patient's legs lean on a cushioned box to flatten the pelvis and the lower back. To study the hip, the patient's foot is placed in a brace that turns the hip inwards. In both cases, the detector passes slowly over the area, generating images on the computer screen.

You should remain completely still and might even be asked to hold your breath for a few seconds as the X-ray images are taken in order to reduce the chance of a blurred image. The technician stands behind a wall or in an adjacent room in order to activate the X-ray machine.

Peripheral tests are simpler. Fingers, hand, forearm or the feet are placed in a small device that obtains a bone density reading in just a few minutes.

The bone density test generally takes about 10 to 15 minutes, depending on the equipment used and the parts of the body being studied.

Photographs

Preparation and advice

Bone density tests are fast and painless.

You can eat normally the day of the test. However, calcium supplements should not be consumed for at least 24 hours prior to the test.

You should wear comfortable, loose clothes, avoiding zippers, belts and metal buttons. Objects such as keys and wallets should be removed from pockets since they could interfere with the area being studied.

You might be requested to remove part of or all of your clothes (a hospital gown is provided) as well as jewellery, dentures, contact lenses and any metal object or article of clothing that could interfere with the X-ray imaging.

Your physician should be informed if you have recently been tested using barium or if you have been injected with a contrast liquid for a CT scan (Computerized Axial Tomography) or a radioisotope. You therefore might have to wait between 10 to 14 days in order to have a DEXA test performed.

Women must always inform their physicians and X-ray technician if they are pregnant or possibly pregnant. Many imaging tests are not performed during pregnancy since radiation could be harmful to the fetus. In the event that an X-ray is necessary, precautions are taken to minimize the baby's exposure to radiation.

TYPES
  • Bone densitometry