A device for determining preferred directions in biological structures by ultrasonic examination. The device comprises an electroacoustic converter which is sub-divided into at least four sectors and which comprises transducers which are combined in groups in sectors which are diametrically situated with respect to the center. The transducers of each group are connected to the inputs of an adder. The outputs of the adders are connected to an arithmetic circuit which is adapted to form a first signal which is dependent of the sum of all signals generated by the transducers, and to form also a number of second signals which are dependent of the differences between signals generated by different transducer groups. The arithmetic circuit is connected to a display device for color images in a manner so that the first signals determines the brightness of the image, while the second signals determine the color information.