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Acquisition of radiological images
Patients have the following procedures to provide images for Radiological
decisions to be made.
Projection radiography
Radiography
Radiographs (or Roentgenographs, named after the discoverer of X-rays, Wilhelm
Conrad Roentgen (1845-1923)) are often used for evaluation of bony structures
and soft tissues. An X-Ray machine directs electromagnetic radiation upon a
specified region in the body. This radiation tends to pass through less dense
objects (skin, fat, muscle, and other tissues), but is absorbed or scattered by
denser materials (bones, tumors, lungs affected by severe pneumonia). Radiation
which has passed through a patient then strikes a cassette containing a screen
of fluorescent phosphors and exposes x-ray film. Areas of film exposed to higher
amounts of radiation will appear black or dark gray after development. The
unexposed areas of film remain white. In Computed Radiography (CR), the x-ray
photons are captured by phosphors within a cassette, which are then read-out by
a scanning machine to give an electronic rendering of the image. In Digital
Radiography (DR) the radiation strikes a plate of minute sensors yielding a
digital image, which is then transmitted and stored by computer and viewed on a
computer screen. In the U.S. all three modalities for obtaining images are
currently in use, although the trend is away from film and toward digital
imaging.
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