High-resolution imaging and tissue characterization using a miniaturized ultrasound probe mounted on a puncturing needle

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In this study, a high-frequency miniaturized ultrasound probe mounted on a puncturing needle and an imaging system for this probe have been developed. The usefulness of this imaging system has been evaluated in in vitro and in vivo experiments. We have also studied the feasibility of tissue characterization using ultrasound attenuation in a high-frequency region. The following results were obtained.Development of the miniaturized ultrasound probe and imaging system A miniaturized probe mounted on a 16-20 gage puncturing needle that can be stuck into a tissue has been developed. A 2-D ultrasound image was obtained by the developed imaging system within about 6 seconds. Practical usefulness of this system was examined by phantom and animal experiments.Detection of blood flow in a small vessel using a correlation technique The imaging system was applied to the detection of blood flow using a correlation technique in a small vessel at deep portion of a body. To evaluate this flow detection method, we carried out in vitro and in vivo experiments and confirmed that flow in a tube of 0.35 mm in inner diameter can be detected.Attenuation measurement in 5-40 MHz and study on mechanisms of attenuation in biological tissue To show a feasibility to characterize a biological tissue from its frequency dependence of ultrasound attenuation, we developed a wide-band attenuation measurement system. From the results of measurements, it was concluded that ultrasound attenuation in a biological tissue is mainly due to tissue-organizing substances, such as protein and water, and the macroscopic structure of a tissue such as muscle fibers and that the cell structure of the tissue little contribute the attenuation.