Twenty years’ development of acoustic microscopy for medicine and biology

Since 1985, scanning acoustic microscope (SAM) systems for medicine and biology has been developed and have been equipped for investigation of acoustic properties of various organs at Tohoku University. There are three objectives of SAM for biomedicine. First, it is useful for intraoperative pathological examination because staining is not required. Second, it helps understanding lower frequency ultrasonic images such as echography or intravascular ultrasound because SAM provides microscopic acoustic properties. Third, it provides information on biomechanics of tissues and cells. The most important feature of our SAM is to measure attenuation and sound speed of soft tissues by analyzing the frequency‐dependent characteristics of amplitude and phase. Recently, a new‐concept acoustic microscopy using a single pulsed wave instead of burst waves used in conventional SAM systems was proposed. Application of SAM has also been broadened and it covers not only myocardium and atherosclerosis in cardiology but also...