radiology image formation & quality Flashcards
In conventional film, which chemical is present in the emulsion?
Silver Halide (makes the film turn black)
What is the advantage of having a double emulsion in radiographic film?
It increases the sensitivity and reduces the dose required.
What are 2 examples of rare earth phosphors used to make radiographic screens?
- Gadolinium
- Lanthanum
What are the 3 things screen speed depends on?
- Thickness of the phosphor layer.
- Crystal size (larger crystals indicate faster film)
- Conversion efficiency.
What is latent image formation?
Unable to see with the naked eye.
State the 5 steps of processing.
- Development
- Intermediate Washing
- Fixing
- Final Washing
- Drying
2x wash stages
What occurs during the development aspect of processing?
The silver halide molecules present in the emulsion turn into silver.
What do the black areas on an X-ray indicate.
Areas where there are no silver deposits.
What is the purpose of intermediate washing phases?
Stops the developing process by washing off the developer.
What might occur if the developer was left on the film for too long?
The whole emulsion would be converted.
What occurs in the fixing stage?
Removes any unreacted silver halide crystals.
(without this, the image would turn foggy)
What is the purpose of the final washing stage?
To remove the fixer.
What would happen to the film if the fixer wasn’t removed?
The film would go brown as it reacts with silver, producing SILVER SULPHIDE.
What does the drying phase of processing do to the film?
Hardens the emulsion.
What are the 3 main film faults?
- overexposure
- overdevelopment (increased time, temp and concentration)
- fogging
Why might a film be pale?
- Under-exposure.
- Under-development.
- Film back to front.
Why may a film be opaque?
- Due to inadequate fixation/exhaused fixer solution.
- Leaves unreacted Silver Bromide crystals on the film.
What may cause a brown film?
Inadequate final washing leading to the formation of silver sulphide.
What could cause double imaging on a phosphor plate?
Where the previous image hasn’t been wiped off before use.
How are phosphor plates wiped of pervious images?
White light is put on top.
What are the 6 aims of quality assurance programmes?
- Consistently high standard.
- Reduce repeats.
- Determine errors.
- Increase efficiency.
- Reduce costs.
- Reduce dose.
How is image quality of radiographs assessed?
Previous grading of 1-3 (excellent, diagnostically acceptable and unacceptable).
*Nowadays, just acceptable and unacceptable is used. findings recorded in the image quality log)
What is the coin test in radiology quality assurance?
- Tests the light-tightness and safelight in a darkroom.
- Involves withdrawing an opaque cover at 30 second intervals.
How often should a radiology audit be completed by someone within the practice other than the person responsible for QA?
Once every year.
How often should a radiology QA audit be carried out by someone external to the practice?
1 audit every 3 years.
