Using a multi-rod waveguide system to create an ultrasound endoscope for imaging in aggressive liquids

The use of traditional ultrasound imaging systems in critical conditions, for example at high temperature, in the presence of chemically active media or increased radiation levels, is often impossible. An approach based on the concept of an “ultrasound endoscope” to remotely display the area of interest through a long bundle of solid rods is proposed. Each rod serves as a waveguide that transfers an ultrasonic pulse from one end located in an aggressive medium to the other end located at a distance in favorable conditions. The diameter of the rods is less than the wavelength to ensure that the ultrasonic pulses used to form the image propagate as the lowest-order longitudinal mode, which is almost non-dispersive and much faster than other possible modes (bending and torsional motions). The results of studies of the 1024-channel waveguide system of megahertz range made of a bundle of stainless steel rods are presented. The obtained images of millimeter-sized scatterers in water demonstrate feasibility of the proposed system.