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Definition: radiology from Philip's Encyclopedia

Medical speciality concerned with the use of radiation and radioactive materials in the diagnosis and treatment of disease. See also radiography; radiotherapy

Summary Article: Radiology
From Encyclopedia of Global Health

Radiology is a branch of medicine whereby radiologists use medical imaging technologies to diagnose and sometimes treat particular diseases. Originally, it was largely connected with the use of X-ray machines and similar devices to photograph parts of people to assist doctors in diagnosis, but is not the radiology involving a wider range of machines and imaging devices.

Radiology began after a German professor of physics, Wilhelm Conrad Röntgen, discovered X-rays in his laboratory in the University of Würzburg on November 8, 1895. Within several months of this medical breakthrough, there were attempts to produce film of moving objects in hope that radiology might be able to depict function. However, this led to technical difficulties because of the very much higher doses of radiation required for moving film, preventing this technique from being developed. However, the X-rays provided such a breakthrough in medical technology that within 10 years, radiology was being used in many parts of the Western world. As a result, Röntgen received the first Nobel Prize in Physics in 1901, with the first English-language book on chest radiography being published in 1905.

Essentially, the X-ray machine provides an image whereby doctors can evaluate bony structures and soft tissues, as well as spotting foreign bodies in tissue. This led to the radiodiagnosis becoming common with the ability of X-rays to penetrate tissue, managing to show up some substances to fluoresce, as well as preserving the situation with a photograph. With the X-rays being able to penetrate tissue, the radiation is absorbed differentially, dependant on the densities of the tissues concerned. As a result, the photograph taken can show a notable contrast between the images of structures and organs, even though these X-rays do not differentiate on their images between adjacent areas of soft tissues. The development of X-ray techniques and technologies by radiographers has meant that contrastmedia can be injected into blood vessels and the effect of them will be seen in X-rays showing the media in arteries, veins, kidneys, and urinary tracts.

The work of radiographers has also changed from simply photographing a patient to providing a more detailed diagnosis.

In the first 20 years following the discovery of X-rays, the role of radiologists changed dramatically with the X-ray machines being used to treat fractures of bones and also for the localization of foreign bodies in tissue, especially bullets lodged in people’s tissue during World War I. The work on locating and extracting bullets led Maria Curie to push for the mobile radiography units to be established to treat soldiers, with her personally providing radon tubes for the French Army. In 1920, the Society of Radiographers was formed, and radiology continued to develop in many ways.

In 1937, a patient suffering from leukemia was treated at the University of California, Berkeley, using radioactivity to treat cancer for the first time. In the same year, Joseph Gilbert Hamilton started to use radioactive iodine for the diagnosis and treatment of thyroid disease. By the 1950s, the work of radiographers had changed to include work on the electronic method which was devised to intensify the image with an image intensifier, overcoming earlier technical difficulties to make cineradiography become more common.

Photographic techniques also improved with the single-coated photographic plates being replaced by double-coated photographic film, with sufficiently good definition, allowing the photographs to be taken at a higher speed, reducing harmful radiation techniques. The developing of photographs has also been sped up with automatic processors able to develop dry film in less than 90 seconds. This, in turn, has meant that if radiographers spot anything serious, they are able to take another photograph or set of photographs almost straightaway without the cost of bringing the patient back at a later time, as previously happened.

A new X-ray device was introduced during the 1970s which revolutionized the work of radiographers. The computerized axial tomography (CAT scan) was devised by the British electrical engineer Godfrey N. Hounsfield and South African-born U.S. physicist Allan Cormack. This measures the attenuation of X-rays entering the body from different angles. Collating these measurements, a computer then reconstructs the organ in three dimensions which allows soft tissue such as liver and kidneys to be easily differentiated in the images that are provided. This led to Hounsfield and Cormack winning the Nobel Prize for Physiology or Medicine in 1979. These CAT scanners are now used in large hospitals and medical centers around the world.

At the same time as the CAT scanners, there was a development in ultrasound to visualize soft tissue structures. An advantage of the use of ultrasound is that unlike normal X-ray radiography, CAT scans, and the recent developments in nuclear medicine imaging techniques, the ultrasound does not use ionizing radiation and therefore is far safer to use. Ultrasound is generally used where other methods may cause problems, such as diagnosing any potential problems in unborn children. However, the major change has come in the added use of the radiation generated for the treatment of cancer and also other conditions.

The next development in work in radiography is with the emergence of magnetic resonance imaging (MRI), sometimes called nuclear magnetic resonance (NMR), with radio waves being beamed into an individual who is being subjected to a powerful magnetic field. As different atoms in the body absorb the radio waves at varying frequencies, a computer can collate the data and then construct images of internal parts of the patient. This has been developed further in nuclear medicine with the patient swallowing particular radioactive tracers such as Technetium-99m, Iodine-123, Iodine-131, and Xenon-133. There is also posi-tron-emission tomography (PET) scanning whereby particles of antimatter are injected into a body which is then scanned.

While the work of radiographers has changed considerably with the development of new machines, the same aim of the original X-ray machine developed by Röntgen remains, with the branch of medicine including radiography becoming hugely important, with the developments making it not only faster and more accurate, but also with the ability to cope with moving images and three-dimensional images.

  • Radiologist; Roentgen, Wilhelm.

  • Eric J. Hall, Radiology for the Radiologist, 3rd ed. (Lippincott, 1988).
  • William S. C. Hare, Clinical Radiology for Medical Students and Health Practitioners (Blackwell Science Asia, 1999).
  • Justin Corfield
    Geelong Grammar School, Australia
    Copyright © 2008 by SAGE Publications, Inc.

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