DYNAMIC CHANGES IN THE ACOUSTO-MECHANICAL AND STATISTICAL PARAMETERS OF TISSUE DURING HIGH INTENSITY FOCUSED ULTRASOUND (HIFU) TREATMENT

Abstract

High intensity focused ultrasound (HIFU) induces focalized tissue coagulation by increasing the tissue temperature in a tight focal region and has been successfully used as a new technique of tumor treatment or to stop bleeding in clinical applications. The main challenges of this technique are: adjusting the location of HIFU thermal ablation exactly at the region of interest, and controlling the level of thermal ablation. Several imaging methods have been proposed to monitor HIFU-induced thermal lesions such as X-ray, MRI and ultrasound imaging. Currently, ultrasound imaging techniques that are clinically used for monitoring HIFU treatment are standard pulse-echo B-mode ultrasound imaging, ultrasound temperature estimation, and elastography-based methods. This study was carried on ex vivo animal tissue samples. Backscattered radio frequency (RF) signals were acquired in real-time including before, during and after HIFU treatment. In this study, first we estimate the dynamic changes in the acoustical, mechanical and statistical parameters of the tissue resulted from HIFU exposures with three different acoustic powers. Then, we use these parameters to detect the induced HIFU thermal lesions and monitor the treatment process. By estimating the standard deviation of the studied parameters along acquired RF data frames, we show that there are significant changes in the tissue properties during the HIFU treatment.