Structured Noise Removal By Using A High Flexible 2D Fir Digital Filter
R. Hecker, Siegfried J. Pöppl · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1982
Depending on the adjustment of data acquisition devices, medical images may be degraded by structured noise, which has to be removed before further steps of image processing techniques like contour finding or feature extraction are applied. In the 2D frequency domain of an image, structured noise usually is characterized by a pattern with relatively sharp bounded regions. So, to loose not too much image information by filtering, it is necessary to apply a digital filter, whose bandstop-region has nearly the same pattern as the structured noise region. In this paper, a polynomal approximation algorithm within the scope of the window method of designing 2D Finite-duration Impulse Response (FIR) digital filters is presented, with which it is possible to design lowpass-, highpass-, bandpass-, and bandstop-filters of arbitrary shape, size and position in the 2D frequency domain. The effect of enhancement by this method on a 2D-echocardiogram degraded by ripple structured noise is demonstrated.