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IMAGE ARTIFACTS What is an ARTIFACT • Any irregularity on an image that is not caused by the proper shadowing of tissue by the primary beam. • an undesirable optical density on radiograph How are they produced? •Exposure •Processing •Handling & Storage ARTIFACT FROM EXPOSURE Associated with conducting Exam • Equipment Incorrect film screen match or poor contact Warped or dirty cassettes Grid misalignment • Patient preparation or instruction (motion) positioning errors technical errors ARTIFACTS FROM PROCESSING Pressure marks from transport of film produced during processing and will usually appear with a higher OD • Roller Marks • Dirty Rollers • Chemical Fog • Wet-Pressure Sensitization ROLLER MARK • Guide Shoes-mark on leading or trailing edge of film, found parallel to the film travel direction. Caused by improper positioned guide shoes or spring shoes • pi lines- 3.1416 inch intervals dirt and chemical stains DIRTY ROLLERS • Emulsion Pickoff • Gelatin buildupsludge • Can appear as sharp positive or negative optical density on film CHEMICAL FOG Improper or Inadequate processing chemistry • Chemical Fog- uniform dull grey – Dichoic Stain- 2 colors yellow, green, blue, purple • Curtain Effect-chemistry running up trailing edge or down leading edge WET PRESSURE SENSITIZATION • Developer tank • Irregular or dirty rollers • Small circular increased optical density HYPO RETENTION • Hypo - fixing agent ammonium thiosulfate • Improper washing • Yellowish discoloration to stored radiograph HANDLING & STORAGE • • • • • • Radiation and Light fog Rough Handling- kink marks Static Hypo retention Kinks Scratches ARTIFACTS FROM RADIATION AND LIGHT FOG • Light leaks • Safelight • Radiation • Heat/humidity below 68 degrees 40 to 60 % humidity HANDLING Before or After processing • • • • Kink marks Scratches Fingerprints Darkroom environment clean dry surfaces STATIC Electron buildup on emulsion Low humidity • Crown • Tree • Smudge CASSETTE BASED FILMLESS ARTIFACTS Digital Radiography and PACS pg 90-98 1. IMAGING PLATE ARTIFACTS • • • • CRACKS –AREAS OF LUCENCY Adhesive tape residue Static causing hair to adhere to plate Backscatter CASSETTE BASED FILMLESS ARTIFACTS Digital Radiography and PACS 2. PLATE READER ARTIFACTS – – – – Extraneous line patterns caused by electronics White lines (horizontal) dirt on light guide of reader Loading of more than one IP into a cassete=double exposure artifact Grid orientation so that grid lines are parallel to the plate reader’s laser scan = moire pattern. (Grids should be high frequency and grid lines need to run perpendicular to the laser scan line CASSETTE BASED FILMLESS ARTIFACTS Digital Radiography and PACS 3. Printer Artifacts – Fine white lines from debris on mirror in printer 4. Operator ARTIFACTS – – – Insufficient collimation = incorrect exposure range (S) reading Backward cassette Underexposure = quantum mottle DR Processing Artifacts • Electronic rather than chemical • Artifacts caused by interference with electronic components CR Handling and Storage Artifacts • • • • • Debris on image receptor Discoloration of fluorescent screens Fogging “ghost images” “dead” detector images Cassetteless Artifacts Digital Radiography and PACS pg 108 • • • • Conversion from x-ray to digital is very fast Potential for signal loss Electronic noise – most typical of artifact Rapid exposures can cause lose of signal=reduction of image quality
