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Radiologic Technologists

History

Radiography uses a form of electromagnetic radiation to create an image on photographic film, or on video or a digital file. Unlike photography, where the film is exposed to ordinary light rays (the most familiar kind of electromagnetic radiation), in radiography the film is exposed to X-rays, which have shorter wavelengths and different energy levels.

X-rays were discovered by Wilhelm Conrad Roentgen in 1895. X-rays, or Roentgen rays, are generated in a glass vacuum tube (an X-ray tube) that contains two differently charged electrodes, one of which gives off electrons. When the electrons travel from one electrode to the other, some of the energy they emit is X-radiation. X-rays are able to pass through skin and muscle and other soft body tissue, while bones and denser objects show up as white images on the photographic emulsion when film is exposed to X-rays. A picture of the inside of the body can thus be developed.

All forms of radiation are potentially harmful. Exposure to ultraviolet radiation may tan the skin, but it can also result in burning and other damage to tissue, including the development of cancer cells. Low-level infrared radiation can warm tissues, but at higher levels it cooks them like microwaves do; the process can destroy cells. Protective measures to avoid all unnecessary exposure to radiation must be taken whenever X-rays are used, because they can have both short- and long-term harmful effects.

There are other forms of diagnostic imaging that do not expose patients to any potentially harmful radiation. Sound waves are used in ultrasound technology, or sonography, to obtain a picture of internal organs. High-frequency sound waves beamed into the patient's body bounce back and create echoes that can be recorded on a paper strip, photograph, video, or digital file. Ultrasound is very frequently employed to determine the size and development of a human fetus. Magnetic resonance imaging (MRI) uses magnetic fields, radio waves, and computers to create images of the patient's body.

The use of imaging techniques that do not involve radiation grew rapidly during the 1980s and 1990s because of the safety of these techniques and because of great improvements in computer technology. Computers can now handle a vast quantity of data much more rapidly, making it possible to enhance images to great clarity and sharpness.

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