A simple method to estimate coordinate resolution and MTF for pixelized detectors

A simple method to estimate the coordinate resolution of pixelized detectors, using non-single photon counting readout is proposed. This method can be useful particularly for testing detectors used in digital imaging systems. The proposal is based on the determination of the statistical correlation between detector neighbor pixels, by means of the statistical noise measurement of isolated pixels, and the linear combination of neighbor pixels. Distributions of differences between neighbor pixels are constructed for pixels sharing an edge or only having one common vertex. The method is validated using images from a GE Senographe 2000D mammographic unit. The pixelized detector has been irradiated by X-rays along its entire surface. The correlation asymmetry between perpendicular directions has been studied to estimate the possible existence of a hardware asymmetry. The coordinate resolution of the studied detector, pixel size 100 μm, is of the order of 50–55 μm, that is, almost twice as large as the value determined by geometry. A small asymmetry between the mutually perpendicular X and Y directions has been detected. The modulation transfer function (MTF) can be estimated from the correlation data, and the reconstructed MTF is in good agreement with measurements.