Processing‐ usually caused by the rollers-Guide shoes, hesitation lines, pi lines, scratches, detection marks, reticulation,
How do radiographs looks like from dirty intensifying screens? (film screen)
Small white spots caused by dust/dirt – periodic cleaning, use screen cleaner
What are the 2 essential components of film?
Emulsion in film is made out of?
microscopic crystals of silver bromide (halide) suspended in a gelatin (extracted from cattle skins) that is coated on both sides of the base
What is best used with rare earth screens and requires a special orthochromatic safelight?
sensitive to yellow-green light
What are the characteristics of film emulsion?
swells during developing step so the electrochemical change can occur to the exposed crystals -> latent image to visible image
shrinks and hardens during fixing step -> permanent image
What are the types of films?
by construction:Screen type (the standard) particularly sensitive to the fluorescent light of the intensifying screen
by sensitivity or spectral ( color) matching: orthochromatic or panchromatic
Orthochromatic film is sensitive to what color light?
Sensitive to yellow-green light - most compatible with rare earth screens
Panchromatic film is sensitive to what color light?
sensitive to red light -- most compatible for laser imaging. Now used for: CT, MRI, digital imaging. Note: manufactured only as single emulsion film
For what procedure are films specially designed for?
What are the 4 major characteristics of film when purchasing?
speed or sensitivity
image receptor contrast
resolution or sharpness of detail
**note: way too many notes to type out so please read about each on lecture notes!
What is the definition of speed or sensitivity?
amount of exposure necessary for the film's emulsion to react to the radiation exposure
Numerical rating scale (notes only)
50 - 100 = slow, detail
200 - 400 = medium
400 - 600 = fast
600 - 800 = ultra fast
Key concept: 400 speed image receptor systems are the most common used today. Exception is tabletop extremities that used 100 -200 speed systems
Speed of film is determined by:
phosphor material: orthochromatic sensitive film is usually faster = less patient dose
crystal size: the larger the crystal size = faster the speed = less dose to patient = decreased image resolution
thickness of phosphor layer: thicker the layer = faster the speed = decreased image resolution but less dose to patient (good ALARA)
What is the definition of contrast?
the visible percentage differences (variations) in the amount of black metallic silver seen in the image. Film manufactures can make film that will demonstrate images with different contrast visualization
high(er) contrast or (lower latitude):
More “black/white type” image or greater visible differences between the density variations (think anatomy) with less number of visible density variations. Good for extremity imaging.
low(er) scale or (higher latitude):
gives an image with more visible shades of density variations. “Less black/white type” image with less visible differences between the density variations (think anatomy) with more number of density variations. Good for chest imaging
Radiographic contrast is manipulated what exposure factor?
What is the definition for resolution or sharpness of detail?
ability of the film emulsion to visibly produce a sharp image. Determined by the speed of the film
What is the rule for resolution or sharpness of detail?
Rule: the slower the speed of the film or intensifying screen or the imaging receptor system the better/increased resolution of the visible radiographic image however patient dose increases (not good ALARA).
What is the definition for latitude?
the margin of error in using the exposure factors to produce a diagnostic image
What are the types or latitude?
wider the latitude = more margin of error (“a forgiving film”), usually this type of film has lower scale contrast
narrower the latitude = less margin of error ( requires greater exposure accuracy), usually this type of film has higher scale contrast