Chapter 12 Flashcards
X-rays that exit the patient and interact with the image receptor
Image-forming x-rays
x-rays that remain as the useful beam exits the patient
exit x-ray beam
medium that convert x-ray beam into visible image
image receptor
emulsion coated on both sides of a film is called the:
double-emulsion film
Ensures uniform adhesion of the emulsion to the base
adhesive layer
the protective covering of gelatin which encloses the emulsion
overcoat
thickness of a radiographic film
150-300 micrometer
the foundation of a radiographic film
base
property of the base
dimensional stability
added to the base of the film to prevent eye strain
dye
original radiographic film
glass plate
types of radiographic film base:
- glass plate
- cellulose nitrate
- cellulose triacetate
- polyester
the standard base, this base is flammable
cellulose nitrate
known as the “safety base”, has the same property with the standard base but its not flammable
cellulose triacetate
the film base choice, it is more resistant to warping from age and is stronger than cellulose triacetate, also permits easier transport through automatic processors
polyester
the heart of the radiographic film
emulsion
emulsion consists of two homogenous mixture
gelatin
silver halide crystals
thickness of a film emulsion
3-5 micrometer
the active ingredient of the radiogragic emulsion
silver halide crystals
silver halide crystal
silver bromide 98%
silver iodide 2%
atomic numbers
iodide = 53 bromide = 35 silver = 47 gelatin = 7
types of silver halide composition
- tabaular
- cubic
- octahedral
- polyhedral
- irregular shapes
most common grain of the silver halide crystal used in the film emulsion
tabular grain
silver halide crystals are made through:
dissolving mettalic silver (Ag) in nitric acid (HNO3)to form SILVER NITRATE (AgNO3)
silver bromide (AgBr) is made through mixing SILVER NITRATE and POTASSIUM BROMIDE (KBr)
the imperfection of the film is thought to be responsible is a chemical contaminant called the
silver sulfide
The contaminant “silver sulfide” is also known as the
sensitivity center
this is where the photoelectrons and silver ions interact to combine
latent imaging center
direct exposure film contains thicker emulsion which explains why DE film is superior/ has greater detail than in a double emulsion film
the size and the concentration of the SHC affects the film speed
high contrast emulsion consist of SMALLER silver halide crystals
low contrast consist of larger grains
larger grains emulsion are more sensitive than SMALL-GRAIN EMULSION
take note
3 critical characteristics of a crossover layer
- absorbs most of the crossover light
- does not diffuse into the emulsion but remains as a separate layer
- completely removed during processing
