本セミナーでは，高周波～超高周波数帯域の超音波を用いた定量超音波診断（QUS; quantitative ultrasound）について，特に眼球や皮膚に関する検討を中心として，最新動向を解説的にご紹介いただきます．

Clinical ultrasound imaging is commonly used to visualize soft tissue morphology. During scanning, a gray-scale B-mode image is displayed on screen from which a trained clinician can evaluate tissue states. However, B-mode image formation images discards high-frequency components in the backscattered echo signal that encode information about tissue microstructure. As a consequence, microstructural changes in soft tissues that accompany disease processes, but do not directly affect tissue morphology, may not be visible in B-mode images. Our group is interested in exploiting the high-frequency information to reconstruct parametric maps that are representative of tissue microstructure. We have particular expertise in very high frequency ultrasound (>80MHz) to assess microstructural properties at the micron scale. In this talk, I will review quantitative ultrasound (QUS) methods based on analyzing the backscatter coefficient and envelope statistics. Then, I will describe applications of high-frequency QUS (80MHz) to evaluate changes in the sclera associated with myopia, followed by an introduction to ultra-high frequency (≥250MHz) quantitative acoustic microscopy (QAM) and demonstrate how QAM can be used to infer the mechanical properties of ocular tissues at <7μm resolution. Finally, I will describe the development and application of a novel high-frequency point-of-care ultrasound device to evaluate myopic eyes in vivo to provide critical information for predicting myopia progression that cannot be done with current clinical ophthalmic measurements.