1Department of Information Processing, Tokyo Institute of Technology, 2Precision and Intelligence Ladoratory, Tokyo Institute of Technology, 3International Cooperation Center for Science and Technology, Tokyo Institute of Technology
Phase of sound pressure is distorted and quality of ultrasonic images is degraded when ultrasonic waves propagate through a inhomogeneous layer. A few studies report experimental measurement of this phase distortion with a linear array transducer. In the present study, we propose an accurate method of measurement that uses a hydrophone. In experiment, soft tissue (porcine liver, meat, and tendon) was placed near the surface of a flat transducer, and distortion of ultrasonic wavefront after propagation through this tissue was reconstructed using an aperture synthesis technique based on sound pressure distribution measured at plane of observation. Influence of both a fluctuation of sound velocity during measurement and a inclination of plane of observation to the plane of transducer surface is compensated for in this data-processing scheme. In addition, this effect was demonstrated by phantom experiments for analyzing the accuracy of this method of measurement.