Multi-scale acoustic characterization over a wide frequency range

To improve the accuracy and stability of current quantitative ultrasound diagnostic technology, it is necessary to understand the relationship between the microacoustic properties of cells and microscopic structural tissues that form the basis of macroscopic ultrasound findings in living tissues. Therefore, we have been promoting the evaluation of acoustic properties of the same tissue using ultrasound across a wide frequency range, with a focus on the liver. We have developed a system that enables echo observation from 1 to 250 MHz by simply changing the transducer using a simple mechanism. However, in ultrasound microscopy at ultra-high frequencies, evaluation results such as speed of sound are highly dependent on the preparation conditions and temperature of biological tissue samples, making it difficult to correlate them with actual biological tissue. To address this, we experimentally verified the effects of sample fixation methodsand sample temperature during actual evaluation and investigated the relationship between sample surface irregularities and signal-to-noise ratio using FDTD simulations. These results are advancing our understanding of differences in frequency dependence of acoustic properties of fat and liver parenchyma in fatty liver disease.