Hygiene Atlas

Atlas · Plate IX · Dental Radiography · 05

Receptors and processing

Digital receptors are either direct sensors (CCD or CMOS) that show an image at once or phosphor plates (PSP) read by a laser scanner. Film still appears on the exam: developer turns exposed silver halide crystals black and fixer clears the unexposed ones. Processing faults have signature looks, from dark overdeveloped films to white fixer spots and fog.

High-yield facts · 9

  1. Digital receptors: CCD and CMOS sensors (wired or wireless, direct, instant image) and PSP phosphor plates (indirect, scanned with a laser).T7
  2. PSP plates should be scanned soon after exposure; bent plates show creases and scratches; light exposure erases the image.T7
  3. A pixel is the digital equivalent of a silver halide crystal; image bit depth sets gray levels.T7
  4. Film emulsion contains silver halide crystals in gelatin; the embossed dot faces the tube (convex side toward the x-ray source).T7
  5. Manual processing: develop about 5 min at 68 F, rinse 30 s, fix about 10 min, wash 20 min, then dry.T7
  6. Developer reduces exposed crystals to black metallic silver; fixer removes unexposed crystals.T7
  7. Overdeveloping or overexposing gives a dark image; underdeveloping, cold developer or underexposure gives a light image.T7
  8. Fixer spots are white; developer spots are dark; light leak or a lit safelight fogs the film.T7
  9. A reversed film shows a light image with a herringbone or tire-track pattern from the lead foil.T7

Facts are written in our own words; each tag links to its source. Values marked "sources vary" differ between references, so check the one your program uses.