Munro,+A.+J.

Munro, A. J. (2005, May 10). //NetDoctor//. Retrieved January 1,, from : http://www.netdoctor.co.uk/health_advice/examinations/x-ray.htm

-"X-rays were first discovered in 1895 when, during experiments with electric currents passed through a vacuum tube, Wilhelm Conrad Röntgen noted that a nearby fluorescent screen glowed when the current was being passed."

-"When the current was switched off the screen stopped glowing."

-"He attributed this effect to previously unknown rays which, X being the symbol for an unknown quantity, he called X-rays."

-"We now know that these rays are, like light and radio waves, a form of electromagnetic radiation."

-"X-rays have high energy and short wavelength and are able to pass through tissue."

-"On their passage through the body, the denser tissues, such as the bones, will block more of the rays than will the less dense tissues, such as the lung."

-"A special type of photographic film is used to record X-ray pictures."

-"The X-rays are converted into light and the more energy that has reached the recording system, the darker that region of the film will be."

-"This is why the bones on an X-ray image appear whiter (less energy passes through) than the lungs (more energy passes through)."

-"In the early days of X-rays, images, such as that of Mrs Röntgen's hand, were produced differently: the bones appeared dark rather than white."

-"Within two months of their discovery, X-rays were being used both in Europe and North America, not just to take pictures of the internal organs of living people but also to treat a wide variety of diseases."

-"The energy that does not pass through the body is deposited within it and it is this energy that causes the biological effects of radiation."

-"The machines used to take X-ray pictures produce X-rays with energies of around 120,000 electron volts."

-"The X-rays used for cancer treatment are much more powerful, with energies of between 2 million and 20 million electron volts."

-"The X-rays are produced by an electrical machine and the patient stands between the machine and a special screen used for obtaining the image."

-"Patients are asked to remove any metal objects, such as watches and jewellery, that might appear on the picture and cause confusion."

-"The patient is asked to keep as still as possible for the few seconds it takes for each image to be obtained."

-"The procedure is entirely painless and there are no side effects."

-"The pictures are checked for technical quality by the radiographer and then sent off to the radiologist for reporting."

-"For more complex examinations this process may take a few hours so the official result of the test is not usually available immediately."

-"A CT (computerised tomography) scanner is a special kind of x-ray machine."

-" Instead of sending out a single X-ray through your body as with ordinary X-rays, several beams are sent simultaneously from different angles."

-"The X-rays from the beams are detected after they have passed through the body and their strength is measured."

-"Beams that have passed through less dense tissue such as the lungs will be stronger, whereas beams that have passed through denser tissue such as bone will be weaker."

-"A computer can use this information to work out the relative density of the tissues examined. Each set of measurements made by the scanner is, in effect, a cross-section through the body."

-"The computer processes the results, displaying them as a two-dimensional picture shown on a monitor."

-"The technique of CT scanning was developed by the British inventor Sir Godfrey Hounsfield, who was awarded the Nobel Prize for his work."

-"CT scans are far more detailed than ordinary X-rays."

-"The information from the two-dimensional computer images can be reconstructed to produce three-dimensional images by some modern CT scanners."

-"They can be used to produce virtual images that show what a surgeon would see during an operation."

-"CT scans have already allowed doctors to inspect the inside of the body without having to operate or perform unpleasant examinations."

-"CT scanning has also proven invaluable in pinpointing tumours and planning treatment with radiotherapy."

-"The CT scanner was originally designed to take pictures of the brain. Now it is much more advanced and is used for taking pictures of virtually any part of the body."

-"The scanner is particularly good at testing for bleeding in the brain, for aneurysms (when the wall of an artery swells up), brain tumours and brain damage. It can also find tumours and abscesses throughout the body and is used to assess types of lung disease."

-"In addition, the CT scanner is used to look at internal injuries such as a torn kidney, spleen or liver; or bony injury, particularly in the spine. CT scanning can also be used to guide biopsies and therapeutic pain procedures."