factors affecting digital image quality Flashcards
factors affecting image quality
- radiographer
- XR machine
- detector
- reader
- storage + compression
- monitor
- exposure factors
- CR reader
- quantum mottle
- spatial sampling
- exposure indices
what happens when exposure factors too high
burnout
what happens when exposure factors too low
quantum mottle
- poor signal to noise ratio
what is detected leaving phosphor plate in CR reader
more visible light detected leaving plate which means we read more signal/ make detector more sensitive
advancements in CR - dual side readout
- light emitted in all directions from plate
- only light towards guide is detected
what is lossy compression
- loss of image quality to gain greater file compression
- better for storage
advantages of lossless compression
- can recover raw data
- most software can read file
cons of lossless compression
- more processing power needed to read larger amount of data
- slower transfer over networks
- can be too large for portable storage media
what limits our spatial resolution in DR
- pixel size
- no pixels in film so resolution really limited by size of photon
- can make pixel smaller than photon
what does out sampling rate need to match
matrix size otherwise have pixels with no signal
what is geometric unsharpness
loss of definition around edges of objects in radiographic images
when does geometric unsharpness occur
- due to factors such as focal spot size, source image distance + object image distance
when does movement unsharpness occur
- due to patient movement during exposure time
what are images more susceptible to at low signals/doses
noise (quantum mottle)
DR vs CR
DR detectors are better + more capable of producing good quality images w/ greater exposure range
