Lecture 4 conventional radiography Flashcards
Cassette ?
Light proof holder for the film
Front side : Facing the x ray source
made of plastic with low atomic number
Back side : made of heavy metal , minimize backscatter radiation
What to maintain the close contact when the cassette closed ?
Compression device such as felt or rubber use
what is an Intensifying screen ?
It is increase the efficiency of x-ray absorption and decrease the dose to the patient
Depending on the phosphor used, the screen will emit light in the blue or green spectrum
4 layers of intensifying screen construction ?
Protective coating : Layer closest to film
about 10 - 20 micrometers thick
Phosphor layer : Active layer and emits light
Reflective layer : redirects the light to film ( 25 micro meters)
Base : Provides support , Farthest from film (1mm thickness) ( it is flexible)
Made of reflective material “magnesium oxide or titanium dioxide” and redirects the light from the phosphor toward the film ”increasing the efficiency of the intensifying screen is ?
Reflective layer
Made up of crystals embedded in a clear plastic support layer
and It convert incident x-ray photons into visible light photons ( active layer)?
Phosphor layer
It is advice used to reduce the level of scatter radiation reaching the image receptor is
or
whose direction is on straight line from source to image receptor is ?
Grid ( which improves image quality)
2 components of Grid ?
Lead strips (grid material)
Aluminum strips (interspace material)
2 types of Grid ?
Stationary
Moving (grid is moving while x ray exposure is being made)
Film construction ?
Consist of two parts: base and emulsion
Most of x-ray film are double emulsion.
Provides a surface and support for the emulsion , It must have strength, but be flexible
Most film bases are composed of polyester
It can tolerate higher temperatures and more fireproof is ?
Transparent base
Glue emulsion to the base
To ensure uniform adhesion of the emulsion to the base and
allows the emulsion and base to maintain proper contact during processing is ?
Adhesive layer
Consist of homogenous mixture of gelatin and silver halide crystal
The gelatin acts as a suspension agent and prevents the crystals from adhering to one another also ( active layer) is?
Emulsion layer
Has designed to be sensitive to different wavelengths is ?
Emulsion layer
Blue sensitive also called panchromatic
green- sensitive also called orthochromatic
Protect the emulsion from scratches, pressure and contamination is ?
Overcoat layer ( protective layer)
What is latent image formation ?
When the image is not visible
The Gurney-Mott theory says that X-rays and light ionize atoms in a crystal that Free electrons move to a sensitivity speck attracting silver ions (Ag+)
what creates latent image ?
When silver atoms gather at the sensitivity speck, the crystal’s charge changes
and
Pattern of exposed and unexposed crystals in undeveloped film formed by how the patient absorbs radiation
What makes radiographic image visible ?
Developing turns silver ions in exposed crystals into black metallic silver
Film speed ?
The speed of an X-ray film is its ability to respond to exposure, determined by its sensitivity
which depends on the size of silver halide crystals, the number of sensitivity specks, and the thickness of the emulsion
Larger crystals, more specks, and thicker emulsion increase the film’s speed
Types of Film ?
All specialty films are single-emulsion
It provides better resolution than double-emulsion film
Mammographic Film
Duplication Film: designed to be sensitive to ultraviolet (UV) light from the duplicating machine
What provides better resolution ?
Single - Emulsion film
It is the mark or spurious image that sometimes appear on the processed film is ?
Artifact
Radiographic film is sensitive to ?
heat and humidity ( Heat reduce the contrast and increase fog and decrease the image contrast )
Light ( should handled in dark , if low level light exposes the film fog increased )
Radiation ( Ionization radiation other than useful beam create artifact by reducing contrast and increasing fog )
Safe lights ?
For blue-sensitive film, an amber filter (transmitting light above 550 nm) is used
For green-sensitive film, a red filter (transmitting above 600 nm) is needed to prevent fogging
How to process automatic film processing ?
Turns the invisible latent image into a permanent visible one by reducing silver ions in exposed crystals to black metallic silver
The silver appears black due to its tiny crystal size scattering light ( instead of reflecting it )
Processing involves four essential stages: developing, fixing, washing, and drying, to create a diagnostic-quality radiograph
Developing ?
Is a water-based chemical solution that reduces exposed silver halide crystals to metallic silver while leaving unexposed crystals unchanged
It uses phenindione and hydroquinone:
Activator: Keeps the developer alkaline.
Restrainer: Limits the reducing agent’s action
Preservative: Prevents oxidation of reducing agents.
Hardener: Maintains gelatin thickness and hardens the emulsion; lack of it causes soft, moist films.
Solvent: Dissolves chemicals, usually filtered water
What agents uses quickly enhancing fine details and gray shades but not heavily exposed areas ?
Phenindione
What agent acts slowly, creating dark, dense areas ?
Hydroquinone
Fixing ?
The fixer stops the developer’s action and removes unexposed silver halide crystals, preparing the film for archiving
Also known as clearing agent : ammonium thiosulfate, ensures the film is clear and durable
If not fully removed, the film appears milky and won’t last under archival conditions
Other chemicals aid in the fixation process
Activator:
Acetic acid maintains the pH to enhance the clearing agent
Preservative:
Dissolves silver from the ammonium thiosulfate
Hardener:
Prevents scratches and abrasions/cuts during processing
Solvent:
Dissolves other chemicals
Washing ?
The washing stage removes any remaining chemicals
If developer or fixer is left, it can oxidize and turn the film brown
Clean water is continuously circulated to ensure thorough washing
Unremoved fixer can react with metallic silver, causing stains like silver sulfide or dichroitic stains (hypo retention)
