Ch. 12 Bushong

Computed Radiography

• CR is a form of digital radiography.

Terms

• IP = imaging plate
• PD = photodiode
• PMT = photomultiplier tube
• PSL = photostimulable luminescence
• PSP = photostimulable phosphor
• SP = storage phosphor
• SPS = storage phosphor screen

The Computed Radiography Image Receptor

• Photostimulable luminescence
• Image receptor: PSP screen inside a cassette
• Light-stimulation—emission
• The diameter of the laser beam determines the spatial resolution of the CR imaging system.

The Computed Radiography Reader

• Mechanical features:
  • Slow scan driver
  • Fast scan driver
• Optical features:
  • Laser intensity control
  • Scatter of stimulating beam
  • Light quanta emitted by screen
  • Light quanta collected
• Computer control:
  • Sampling
  • Quantization

Imaging Characteristics

• 4 principal characteristics:
  • Spatial resolution
  • Contrast resolution
  • Noise
  • Artifacts
• Image receptor response function
• A 14-bit CR image has 16,384 gray levels.
• Image noise, Scatter