Abstract: An ultrasonic transducer for use in locating devices with an ultrasonic imaging system which is sensitive over a broad range of angles of incident acoustic beams, such as those beams emitted in ultrasonic systems, has a curved surface, and is an annular member in shape. The elongated catheter or other device passes through the opening of the annular transducer. Based on the shape of such transducers and the wavelength used, the response of the transducers is a function of the angle of the insonifying beam to the catheter axis. The particular response of such transducers is shown to depend on the curvature of the annular marker, with the radius of curvature chosen on the basis of the wavelength used in the ultrasonic scanning system; between 2-50 wavelengths.