Fig. (1) Echo processing scheme. In the beam former, echoes from tissues are converted to electric signals by piezoelectric transducers PT, which are added in phase through delay lines DL and amplified by TGC. Echo signals are then demodulated, filtered and compressed in the signal processing section. In the image processing section, echoes are firstly converted into numeric values and arranged in the image matrix by the scan converter (pixels) and then pre-processed. After image has been saved, image pixel are postprocessed and displayed.