A computer simulation of wavelet noise reduction in computed tomography.

We describe the use of a graphical mathematical spreadsheet programming environment which can be used to simulate the acquisition and reconstruction processes of an x-ray computed tomography (CT) machine. The simulation is used to study the effect of photon counting statistics on the noise in the reconstructed image. Finally we describe and evaluate a novel technique for noise reduction using a nonlinear wavelet filter in which the filter thresholds are calculated individually from the "measured" projection data. This filter is shown to compare favorably to threshold filters based on global estimates of noise variance.