Comparison of acoustic properties in various rat organs using high frequency ultrasound

Acoustic property of tissue such as speed of sound (SoS), attenuation provide beneficial information for the pathological diagnosis. The pathological change due to liver fibrosis have been investigated by using a 250-MHz central frequency transducer with fine spatial resolution of 4-μm. The SoS and attenuation of rat liver in case of control and fibrosis models were measured by bioacoustics microscopy incorporating the 250-MHz transducer. In addition, rat spleen was measured to investigate whether tissue property in spleen was affected by liver fibrosis. The SoS and attenuation were calculated by analyzing the echo data in frequency domain, and their 2D images were obtained by scanning the transducer. After the measurement, the histology in the same cross section (H&E staining and Azan staining) was acquired for comparing with 2D image of acoustic properties. Rat livers and spleens of the control and fibrosis model were measured. In case of liver, there were the individual variability for SoS and attenuation. In a sample of fibrosis model, for example, the difference of SoS between normal and fiber portions were approximately 50 m/s. In contrast, there was no significant difference between them in another case. In addition, there was few difference between control and fibrosis models. In case of spleen, we clearly found the significant difference in SoS and attenuation between white pulp and red pulp. However, there was few difference between control and fibrosis models as well as the liver.