How to Process Radiographs Flashcards
What is processing
- Processing refers to a series of steps that facilities the production of a visible permanent image on a radiograph.
- Latent image converted to visible image
What are the general types of digital and conventional radiography
Digital = direct + indirect Conventional = manual + automatic processing
Describe direct digital radiography
- Uses a solid state sensor to capture the image
- Image is produced electronically immediately following the exposure of the digital sensor to radiation
Describe indirect digital radiography
Uses a Photostimulable Phosphor Plate (PSP)
Following exposure to radiation, the digital sensor has to be scanned by laser in a separate step before the image is produced electronically.
Describe conventional radiography
- Photographic film is exposed to radiation
- Film requires processing using a chemical
process before the image can be viewed - Processing can either be undertaken manually or by means of an automatic film processor.
How do digital sensors work, like how can do they represent each part of a patient
- Uses a matrix (cube split into squares) to represent an image and the image is made up of several pixels.
- Each pixel represents a 3D voxel (cuboid) of the patient
- The depth of this voxel depends on the thickness of body part imaged
What types of conversion detector are used in digital solid state detectors
Direct conversion detectors - Thin Film Transistors (TFT)
Indirect conversion detectors - Charge-coupled devices (CCD) or TFT to read image
These are directly connected to a computer
What are the layers of a solid state detector
Scintillation Layer
P-type silicon
N-type silicon
Insulating layer
How is the latent image formed using a direct digital solid state detector
X ray photons –>
Scintillation layer –>
X-ray photons converted to light –>
Light interacts with silicon by the photoelectric effect –>
Charge packet in each individual pixel –>
Latent image
How is the latent image converted into an actual picture
- The latent image is read by the computer via an analogue to digital converter
- Digital images are saved in shades of grey
- Grayscale value (level of grey) of the radiographic image produced is proportional to the amount of x-ray energy absorbed by the tissue.
What values can a pixel have on the grayscale and what does a high/low value represent
Grayscale values are between 0 and 255.
Values closer to 0 are darker and represent structures with less attentuation of the beams like soft tissues.
Pixels closer to 255 are lighter and represent structures with high attentuation like bone or teeth
How is an image formed using a phosphor plate in indirect digital radiography
- Phosphor layer absorbs and stores energy that has not been attenuated by the patient
- Plate is then scanned by high energy laser beam and stored energy is released as light photons
- Light is detected by a photomultiplier tube in the CR (indirect?) reader and converted into electrical signal
- Input into the computer via analogue to digital converter
- Plate is cleared ready for reuse
- Not directly connected to computer
What is used to clear the phosphor plate
White light
List the layers that make up a phosphor plate
- Protective layer
- Phosphor layer
- Anti-halo and reflective layer
- Base
- Backing layer
What is the purpose of the lead layer in the film thing
Absorbs scatter and radiation
What are the tracks on the lead film for
If you put the film in the wrong way around you will see artefacts in the x ray of these tracks to let you know that you’ve fooked it
So what are the layers that make up the package that the film is given in
1 - front cover 2 - black paper 3 - film 4 - black paper 5 - lead 6 - back cover
What are the layers of the film layer of the package ting
Protective layer (gelatin) Emulsion (silver halide) Adhesive Plastic base Adhesive Emulsion (silver halide) Protective layer (gelatin)
What happens to the silver halide crystals when x rays fall on them
They are sensitised and so some in the film are sensitised and some are un-sensitised
What is film processing
Accelerates the reaction occurring in the silver halide as a result of light/x-ray exposure.
Describe the process of film development in exposed silver halide crystals
- Green silver halide crystals are converted to a black metallic silver
- add developer solution and then wash
- black metallic silver is fixed to the plastic base
- add fixer solution
- wash the fixer off the plastic base
- wash again and then dry bruh
Describe the process of film development in un-exposed silver halide crystals
- Un exposed silver halides are not affected by the developer solution.
- developer is washed off and the un-exposed silver halides are removed into solution leaving the plastic base transparent
- add fixer solution, wash fixer off the plastic base
- wash again and then dry
What are the roles of developer solution in film processing
- Distinguishes between unexposed and exposed silver halide crystals
- Reduces exposed silver halide crystals into metallic silver and creates black areas in the radiograph
- Unexposed Silver halide crystals remain unaffected
- Remaining developer solution rinsed by water or squeezed out by rollers
What is the role of fixer solution in film processing
- Removes the unexposed green silver halide crystals creating white or transparent areas on the radiograph
Why do we need to wash the film at several points when processing
- Removes any traces of the remaining solution
- Failure to remove all chemicals will cause
premature deterioration of the image - After rinsing, the film is dried either by a drier within the automatic processor or by use of drying cabinet or dust-free, well ventilated room.
Describe each step in manual processing (5)
Initial step - unwrap the exposed film and clip film to a hanger
Developing - immerse in developer solution, agitate, 5minutes at 20 C.
Wash - 10 seconds
Fixation - Immersed in Fixer solution, 8-10 minutes
Wash - running water, 8-10 minutes
Dry - Dust free atmosphere
What are the disadvantages of manual film processing
- Time consuming
- Operator
dependent - Fumes
- Hazardous chemicals
- Messy
- Smelly!
How do self developing films work
- X ray film in special sack containing developer and fixer
- After exposure the developer tab is pulled, releasing the solution onto the film.
- After 15s you pull a tab to release fixer onto film
- Used chemicals are discarded and the film is rinsed under running water for 10 mins
What are the disadvantages of using self developing films
- Poor overall image quality
- Image deteriorates rapidly with time
- There is no lead foil inside the packet
- Film is very flexible and easily bent
- Difficult to use in positioning holders
- Relatively expensive
Describe the process of processing that happens inside an automatic processor
- Unwrap the exposed film
- Immerse in developer for 2 mins at 21C, agitate
- Immerse in fixer for 2-3 mins
- Running water for 3-4 mins
- Dust free atmosphere
Name some factors that film processing is dependent on
- Concentration of chemicals
- Temperature of Chemicals
- Development time
- Cleanliness of wash water
- Wash time
- Careful handing of film – before, during and after
- Dust free environment
- Light-tight environment
What will you see if you use too high and too low temps
High - mostly black image
Low - mostly white image
What is light fogging
When the x ray picture turns out black as it was exposed
Difference when exposing film and phosphor plate to light
Phosphor plate - clears it
Film - makes it all black
