X-rays

Written by: 
Dr Roger Henderson

What are doctors looking at on an X-rayA type of electromagnetic radiation used to produce images of the body. and how do the images help with diagnosisThe process of determining which condition a patient may have.?

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X-rays, which have been used since 1895, help to highlight any abnormalities inside the body by painlessly producing pictures of a particular area using radiation.

The X-rays themselves are high-energy bursts of radiation. These pass easily through soft tissue, such as flesh and fatOne of the three main food constituents (with carbohydrate and protein), and the main form in which energy is stored in the body., but they are blocked by dense tissue, such as bone or calciumAn element that forms the structure of bones and teeth and is essential to many of the body's functions.. This allows problems to be shown up that cannot be seen from the outside, such as a broken bone or a shadow on the lung (which suggests a potentially serious condition such as a tumour).

Having an X-rayA type of electromagnetic radiation used to produce images of the body. is painless; you cannot see or feel anything, and there are no after effects

What different tissues look like

Soft tissue and flesh appear as pale grey-white areas on an X-rayA type of electromagnetic radiation used to produce images of the body., while bones and harder structures are white and much clearer to see. Hollow or fluid-filled vessels can also be made visible using a liquid (called a contrast mediumA substance taken (either by mouth or into a vein) by a person who is about to undergo an imaging investigation, to improve the visibility of the structures being imaged.) that is injected into the body or swallowed. X-rays cannot pass through this medium, so areas such as bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. vessels and the urinary and digestive systems can also be shown.

What is the standard procedure?

For most X-rays, you can eat and drink normally beforehand. You are not generally expected to take off your clothes, although you will need to remove any jewellery.

When having the X-rayA type of electromagnetic radiation used to produce images of the body. taken, you will be asked either to lie on a table or stand up so that the part of your body to be X-rayed is between the X-rayA type of electromagnetic radiation used to produce images of the body. machine and a flat film cassette. You then have to keep as still as you can - sometimes holding your breath - and the picture will be taken in a fraction of a second.

The X-rays pass through your body onto the film, which is then developed, either as a conventional film or more often now as a digital photograph. More than one X-rayA type of electromagnetic radiation used to produce images of the body. may be required, taken from different angles.

A radiologist then analyses the pictures and sends a report to your family physician or specialist, depending on who has requested the X-rayA type of electromagnetic radiation used to produce images of the body.. In an emergency an X-rayA type of electromagnetic radiation used to produce images of the body. may be examined immediately, for example to assess an injury.

What can X-rays detect?

A wide range of potential problems can be picked up by an X-rayA type of electromagnetic radiation used to produce images of the body., including:

  • Fractured bones
  • Lung problems such as infectionInvasion by organisms that may be harmful, for example bacteria or parasites. or tumours
  • Thinning of the bones
  • Osteoarthritis
  • Stones in the body (for example, kidney stones)
  • Enlargement of the heart
  • Dental abscesses

Specific X-ray techniques

X-rays are also used in different specialised situations such as:

  • Barium swallow: a radio-opaque liquid (that is, a liquid that the X-rays cannot pass through) is swallowed and a series of pictures is taken at the same time. This technique highlights any blockages or problems in the oesophagusThe gullet, the part of the gastrointestinal system that extends down from the mouth cavity to the stomach. (gullet). A similar process is used when looking at the stomach, when it is called a barium mealAn X-ray examination of the stomach, taken after swallowing a liquid that shows up clearly on the X-ray (barium sulphate).
  • Barium enemaThe introduction of a liquid into the bowel via the anus either to deliver a drug or to wash out the contents of the rectum.: here, the contrast mediumA substance taken (either by mouth or into a vein) by a person who is about to undergo an imaging investigation, to improve the visibility of the structures being imaged. is inserted via the back passage (rectum), and may reveal any problems in the large bowel (the colonThe large intestine.), such as narrowing, inflammationThe body’s response to injury., ulcers or tumours
  • Mammogram: used to look primarily for breast cancerAbnormal, uncontrolled cell division resulting in a malignant tumour that may invade surrounding tissues or spread to distant parts of the body., this simple X-rayA type of electromagnetic radiation used to produce images of the body. shows up cysts and areas of calcificationCalcium deposited in tissues and organs. in the breast as well as tumours
  • CTA scan that generates a series of cross-sectional X-ray images. scanning: a much more detailed type of X-rayA type of electromagnetic radiation used to produce images of the body., which shows up not only bone and soft tissue but also tendons, cartilage and nerves.  See more information on CT scans.
  • Angiogram: contrast mediumA substance taken (either by mouth or into a vein) by a person who is about to undergo an imaging investigation, to improve the visibility of the structures being imaged. is injected into the circulation of one part of the body (such as the heart) to show whether there is any narrowing or blockage present there.

X-rays should be avoided by women who are pregnant. If you have an X-rayA type of electromagnetic radiation used to produce images of the body. and discover only afterwards that you were pregnant, however, the small risks are not enough to justify terminating the pregnancy

Cautions

Because tiny amounts of radiation are used, X-rays are seen as being very safe. However, if large or repeated amounts are used, there is, in theory, a risk of cellThe basic unit of all living organisms. damage, so the dose is always kept as low as possible.

Because the reproductive organs are especially sensitive to radiation, these are shielded during the procedure. Whenever possible, X-rays are avoided if a woman is pregnant.