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A generalization of the E-filter originated by Moore and Parker  from a one-dimensional filter to a nonlinear two-dimensional filter is presented. It is demonstrated that the response of the E-filter is almost independent of the frequency of the incoming signal under certain conditions but depends largely on the signal amplitude. Consequently, it can be used to filter out low-amplitude noise which has been superimposed additively on the signal. The performance of a one-dimensional E-filter as applied sequentially to the rows and then the columns of a digitized image is compared with the direct application of a two-dimensional E-filter. A simple two-dimensional E-filter digital realization and several filtered biomedical images are presented to demonstrate the application of this nonlinear filtering technique.