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Analog (Film) vs. Digital (Computer Radiography) Comparison
Analog Screen / Film Systems
"Rare Earth" screens - Gadolinium Oxysulfide or Lanthanum Oxybromide.
Speed range from 100 to 1000
Very dependent on processing parameters
Reproducibility is nearly impossible due to differences in generators,
processors, positioning, techniques, darkroom conditions.
Over/underexposure usually results in re-exposing patient to ionizing
radiation.
Affected by ambient conditions such as heat, cold, humidity
Cannot be in more than 1 location at a time
Film is the recording, output, and archiving medium.
Image density and contrast are controlled by KVP, MaS, and film type.
Images can only be "hot-lighted" to improve viewing.
Nothing can be done to improve viewing films that have been
underexposed.
2–16
Digital Computer Radiographic Systems
Phosphor screen - Barium Flourohalide.
Screen speed:
• General Purpose (GP), 200 - 250
• High Resolution (HP), 100 - 125
Reproducibility = 100%
Just print another copy of the digital image.
Re-exposure to ionizing radiation because of exposure factors is nearly eliminated.
Not affected by ambient conditions such as heat, cold, or humidity.
CR images can be viewed at numerous locations at the same time, in the same
building or in remote locations.
Recording medium is storage phosphor, output can be film or paper or digital
display, archiving medium is digital.
Density and contrast are controlled electronically by image processing parameters;
however, KvP and MaS are still important image control factors for details and
"noise/mottle" in the digital image.
Digital images can be electronically post processed on a workstation to modify
density, contrast, sharpness, etc.
Much can be done to improve viewing images which may have been poorly
exposed:
• Image density and contract are controlled by pre-set software parameters
12/12/94 – 1234563
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