Film (2,3) Flashcards
Class depends on?
- film speed
- size of silver bromide and silver chloride grains
- contrast
Contrast
Films ability to show density differences
- (high or low)
Classes
Type I
- Type II
- Type III
- Type IV
- Speed is slowest at Type I
- Grain is finest at Type I
- Contrast is highest at Type I
What are radiographic films made of?
An emulsion of gelatin and radiation sensitive silver halide crystals (silver bromide or silver chloride) that coat both sides of the base and layers about 0.0005in thick.
X-Ray Films are sensitive to what?
Light
What happens when developing Radiographic Film?
Ionization disturbs the atomic structure silver bromide in the film causing atoms to enter chemical reactions with one-another producing an image.
Lead Screens
Scattered Photons create a loss of contrast and definition. Exposures above 150Kv place the film between two thin sheets of lead foil screens.
Lead Foil Screens
- Two thin sheets of lead compound evenly coated on a paper backing - essential in radiographic and gamma ray film
- increase the films “photographic action”
What does Lead do to film?
- Lead emits electrons and secondary radiation under the action of X/Gamma rays
- shorter exposure time
- Absorb large portion of scattered radiation intensifying primary radiation (contrast + definition)
Fluorescent Screens
Incident radiation causes these screens to give off light to help expose film
- light produced is in all directions = lower definition
- medical radiography, low Kv
- NOT FOR GAMMA RAYS (RULE)
- Thick specimens