Ch 19 & 21 Image Artifacts Flashcards
What is an image artifact?
Any undesirable OD on an image that does not properly show the anatomy being examined
What is the problem with having artifacts in your image?
- Time
- Money
- Reexposure
How do you determine the cause of artifacts?
By looking at the:
- Patient
- Processing
- Exposure
- Handling & Storage
What are benefits of early detection of artifacts?
- Cost
- Patient dose
What do you do when examining films for artifacts?
- Isolate artifact
- Identity the cause
- Make corrections to eliminate the cause
What are some processor artifacts?
- Emulsion pickoff
- Chemical fog
- Guide shoe marks
- Roller scratches
- Wet pressure sensitization
- water mark
- Chemical spots
What are Pi lines?
- Occur at 3.14 inch intervals
- Due to dirt or a chemical stain on a roller
- Artifact appears perp. to films direction of travel
What do dirty rollers cause?
Emulsion pick off and gelatin buildup resulting in sludge deposits on the film
What are guide shoe marks?
Seen at leading or trailing edge on film caused by improper positioning
What is chemical fog?
- Over development of film
- Developer temp, time, pH too high
What is another name for wet Pressure sensitization?
Entrance roller marks
Chemical fog is typically ______ and across the entire image.
Uniform
What is wet pressure sensitization?
Entrance rollers become wet before film is introduced
*Looks like a water spot
What does a discolored film look like?
Sepia look
-Due to hypo (fixer) retention
What is a Dichroic stain?
Curtain stain that shows up in (2) colors
What causes a brown color in the dichroic stain?
Oxidized developer
What causes a greenish yellow color in a dichroic stain?
Incomplete fixation
What causes hypo retention?
- Incomplete washing
- Has a chalky appearance
What is plus density?
Darker than the background (black)
What is minus density?
Lighter than the background (white)
What causes plus density?
- Caused by physical pressure on the film AFTER it was exposed
- Poor film handling
- Poor loading techniques
- Dropping or bending fo film
What causes minus density?
- Caused by physical pressure on film BEFORE it was exposed
- Artifact was caused before the fixing or washing stage
- Usually dust or dirt on cassette
When does plus density happen?
During development stage
Motion
- Blurring of the image
- Caused by pt motion, x-ray source or IR
Heat blur
Occurs when CR imaging plate is exposed to intense heat before processing with the CR reader system
Double Exposure
IR is exposed more than once before processing
Improper patient position
?
Poor film to screen contact
- Results in localized blurring of the image
- May appear smooth in the area of poor contact on the image
Grid lines
- Shadows of lead strips that appear due to failure of grid to move during the exposure
- Improper grid-focusing distance
- Improper centering
- improper angulation of CR w/respect to the grid lines
Grid cutoff
- A decrease in OD caused by primary radiation being absorbed by the grid
- Caused when patient is placed under the tube when the tube is not centered to the table or Bucky tray
Moire Effect (zebra pattern)
- Double set of grid lines caused by the placement of a grid cassette in a Bucky
- Biggest artifact in MRI
What are some artifacts caused by handling & storage?
- Light fog
- Radiation fog
- Static
- Kink marks
- Scratches
- Dirty cassettes
What is radiation fog caused by?
- Temperature or humidity too high
- Film bin not properly shielded from radiation
- Safelight too bright
- Film left in room during add. exposures
What causes kink marks (crescent mark?)
- Improper handling of film
- Stacking film too high
What causes static artifacts?
- Static electricity
- Temperature or humidity too low
What does a Smudge static artifact look like?
Finger print
What does a Crown static artifact look like?
Crown
What does a Tree static artifact look like?
Brush marks
Generally radiographic artifacts occur in what three areas?
- Exposure
- Processing
- Handling
What are the (3) classification of artifacts in DR?
- Image receptor
- Software
- Object
