Imaging

X-RAYS, RADIATION DOSE AND YOU

What are x-rays?

X-rays use invisible electromagnetic energy beams to produce images of internal tissues, bones and organs on film. Standard x-rays are performed for many reasons, including diagnosing various medical conditions or bone injuries.

When the body undergoes x-rays, different parts of the body allow varying amounts of the x-ray beams to pass through. The soft tissues in the body (such as blood, skin, fat, and muscle) allow most of the x-rays to pass through and appear dark grey on the film. A bone or a tumour, which is denser than the soft tissues, allows few of the x-rays to pass through and appears white on the x-ray. At a break in a bone, the x-ray beam passes through the broken area and appears as a dark line in the white bone.

How are x-rays performed?

X-rays can be performed on an outpatient basis or it may be part of the hospital patient's care. Although each hospital may have specific protocols in place, generally, an x-ray procedure follows this process:

The patient is positioned on an x-ray table that carefully positions the part of the body that is to be x-rayed -- between the x-ray machine and a cassette containing the x-ray film.
Body parts not being imaged may be covered with a lead apron (shield) to avoid unnecessary exposure to the x-rays.
The x-ray beam is then focused on the area to be imaged.
The patient must keep very still or the image will be blurred.
The radiographer then steps behind a protective window and the image is taken.
Sometimes, various x-rays may have to be taken at different angles, such as the front and side view during a chest x-ray.

Are X-rays safe?

Patients are sometimes concerned about the possible harmful effects of radiation, so lets try to explain the risks and put them into perspective.

Medical imaging can be a vital component in making the right diagnosis, and leading to the correct course of treatment. Having an x-ray examination can therefore bring a real benefit to the patient. The concern of your doctor and the hospital radiology department is to ensure that when radiation is used, the benefits outweigh any small risk involved.

Sometimes the risk to your health from not having the examination is likely to be much greater than that from the radiation itself.

X-ray doses

Radiation doses used for x-ray examinations are many thousands of times too low to produce any immediate harmful effects. The only possible effect known from using such low doses is a very slight increase in the chance of cancer occurring many years or decades after the exposure.

To put this small risk into perspective, lets consider that every day of our lives we are all exposed to natural radiation called background radiation. The air we breathe, the food we eat, the houses we live in and the ground we stand on, are all sources of natural radiation. We are even exposed to radiation from outer space called cosmic radiation. Each medical x-ray gives us a small additional dose on top of this background radiation. Depending on the type of x-ray examination you have, your level of dose can range from the equivalent of a few days of background radiation to a few years. This represents only a fraction of our lifetime dose from natural radiation.

Most things we do in life carry a level of risk. The lower the risk of something unpleasant happening - the 'safer' we tend to feel. Airline flights are considered by most people to be very safe, and the risk of a crash is well below 1 in 1,000,000. In fact a four hour plane flight exposes passengers to a cosmic radiation dose the same as that of a chest x-ray.

As long as a clear benefit exists from having an x-ray examination, the risks from the small dose of radiation should usually be outweighed. It should also be remembered that the higher dose examinations are usually involved in diagnosing more serious conditions where a greater benefit to the patient is to be expected.

Your radiographer will make every effort to keep radiation doses as low as possible.

You should make your doctor aware of any other recent x-rays you have had to avoid unnecessary further examinations.

Risks are much lower for older people and a little higher for children and babies.

If you are concerned about the possible risks from having an x-ray ask your doctor how the examination will help with your treatment. If treatment decisions depend on x-ray results then the risk to your health from not having the examination may be much greater than that from the radiation itself.

Information sourced by: Damien Fielden