This article deals with the technical quality assurance of ultrasound B-systems. As part of a mini-trial during the Dreiländertreffen in Davos "Ultrasound 2012", we addressed the question as to whether physicians can detect faulty probes spontaneously during live scanning B-mode. For this purpose a special diagnostic device had been prepared so that groups of piezoelectric elements in the array were without function. Then the images had to be characterized by test persons without knowledge of the faulty elements. The results show that a deterioration of the image could be detected starting at five disabled elements. Due to the small number of test persons, our statements are only preliminary.