Photostimulable phosphor plate technology ( Computed radiography )

  • Photostimulable phosphor plate is a method used to obtain digital X-ray images
  • The Photostimulable phosphor plate is in the form of a cassette which can be used in conventional X-ray machine in place of the X-ray film
  • The X-rays falling on the cassette produces a latent image by exciting the electrons to a higher energy level
  • The image can be read by using a scanning laser beam
  • The electrons release energy in the form of photons when they return to their lower energy level
  • These photons can be detected by using cameras to produce the digital image
  • Photostimulable phosphor plate technology has a more linear optical density vs radiation exposure curve compared to the older film technique (which has a sigmoid curve)
  • This property is useful in obtaining images of structures which vary widely in their radiographic density
  • Another advantage of this technology is that it limits the number of repeat X-rays required due to error in picking the correct exposure level
  • A disadvantage is that it has lower spatial resolution (about 2.5 line pairs per mm) compared to conventional film (about 5 line pairs per mm)
  • But this deficit is more than compensated by its increased contrast resolution
  • The plates can be reused about 1000 times, and hence saves cost on X-ray films and chemical processing
  • Also, it can be used in mobile radiography equipment unlike direct digital radiography which is very heavy and fragile

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