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RAD 350 Chapt . 18 Viewing the Digital Image

RAD 350 Chapt . 18 Viewing the Digital Image. Human eye Rods – scotopic /night vision Cones – photopic /day vision Lumen is the basic photometric unit Luminous Flux – quantity of photometrix Illuminance – intensity of light on a surface. Light Terms con’t.

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RAD 350 Chapt . 18 Viewing the Digital Image

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  1. RAD 350 Chapt. 18 Viewing the Digital Image Human eye Rods – scotopic/night vision Cones – photopic/day vision Lumen is the basic photometric unit Luminous Flux – quantity of photometrix Illuminance – intensity of light on a surface
  2. Light Terms con’t Luminance – brightness of a source of light (computer/tv screen) Inverse Square Law Cosine Law – If you view a screen/monitor from the side, the image is not as good as straight on
  3. Hard vs soft copy Hard copy = radiograph on a viewbox Soft copy = image on a monitor/TV Cathode Ray Tube – digital viewing device Active matrix liquid crystal display (AMLCD) – MUCH BETTER viewing display than CRT Spatial resolution improves with HIGH megapixal display matrix
  4. AMLCD con’t Measure of luminance of AMLCD = aperature ratio AMLCD’s have less noise than CRT’s and better contrast resolution
  5. Pre/post processing Pre-processing the image is automatic – but must have QC on the “system” at least annually Post processing required a PERSON to do Annotation – labeling Windows/level – playing with the grayscale (contrast) Image flip – reorient the image Image inversion – blacks to whites/whites to black
  6. Pre/post con’t Subtraction (DSA) used to make things more visible (improve contrast) Pixel shift – “reregister an image” to correct for pt. motion Region of Interest (ROI) – determine a shade of contrast (gray) to display
  7. PACS Picture archiving & communication system Image acquisition system Display system Network Storage system
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