Which of the following possesses the widest dynamic range? 1)high speed screen, 2)slow speed screen, 3)AEC, 4)CR
4) CR --
One of the biggest advantages of CR is the dynamic range, or latitude, it offers. The characteristic curve of x-ray film emulsion has a certain "range of correct exposure," limited by the toe and shoulder of the curve. In CR, there is a linear relationship between the exposure, given the PSP (photostimulable phosphor, or image plate) and its resulting luminescence, as it is scanned by the laser. This affords much greater exposure latitude and technical inaccuracies can be effectively eliminated. Overexposure of up to 500% and underexposure of up to 80% are reported as recoverable, thus eliminating most retakes. This surely affords increased efficiency; however, this does not mean that images can be exposed arbitrarily. The radiographer must keep dose reduction in mind. The same exposure factors as screen-film systems, or less, are generally recommended for CR.
Intensifying screens used in screen-film x-ray imaging tend to produce high contrast. The faster the screens, the higher the contrast; higher contrast is often associated with decreased latitude. AEC refers to automatic exposure control and is unrelated to dynamic range or latitude.