digital imaging Flashcards
what does kVp control
the penetrating power of the xray beam
quality
what does mA control
the quanity of the xrays
link between kVp and mA
the ‘rule of constant intensity’ means the if you increase the kVp by 15% and halve the mAs the image wil seemingly appear to have received a ‘similar’ exposure
effect of more pixels
fine detail
effect of smaller pixels
increased visibilty
what is bit depth
the number of shades of grey available for image display
no of shades in 2^n
what does digtial image enhcancement do
recoomends exposire factors
most machines have body parts programmed in
role of histograms post processing
allows you to tell if image is under or over exposed
if pushed tot he rigth - underexposed
if pushed to the left - overexposed
what does gamma do in histograms
describes the contrast
generally defects to 1 ie tan45 =1
gamma controls the contrast via LUT curve
what is windowing
limiting data to useful area
spreads coulours out over the same 256 pixels
controls the number of active panles in the image
what is contrast correction
an LUT curve is applied to create teh optimum image
an infinite array of LUT could be applied to suit the potential desires
LUT are programmed in the look-up tbale
what does inverting involve
optimised image can be easiliy inveretd so the colours are swapped around
can make it easier to identify anatomy
what is RGB colour
can give a grenn or blue ting
humans see colour and so image perception increases with colour inclusion
what do low pass filters do
gentle smoothing effect
takes away noise
what do high pass filters do
shaper edges
