It is important to assess image quality, in order to ensure that the imaging system is performing optimally and also identify the weak points in an imaging system. Three parameters mostly leading to image degradation are contrast, spatial resolution and noise. There is always a trade-off between spatial resolution and signal to noise ratio,but in scintillating fiber array detectors spatial resolution is not as important as signal to noise ratio, so we paid more attention to contrast and SNR of the system. By using GEANT4 Monte Carlo detector simulation toolkit, some effective parameters of the linear plastic scintillating fiber (PSF) array as an imaging detector were investigated. Finally we show that it is possible to use this kind of detector to take CT and DR (Digital Radiography) image under certain conditions.