Measurement of internal temperature in biological tissue specimen with deformation by statistical analysis of ultrasonic scattered echoes

Abstract

In this paper, we present the Nakagami shape parameter m estimated by the statistical analysis of ultrasonic scattered echoes from a soft-tissue-mimicking phantom and a soft tissue heated from room temperature up to 42.0 °C. The ratio change of m values for both phantom and biological tissue specimens clearly show temperature dependence. We show changes in the internal temperature of the biological tissue specimens using two-dimensional hot-scale images indicating absolute values of the ratio change of m values. However, in an in vitro experiment using porcine tissue, no clear change of m values was observed with a smaller region of interest (ROI) owing to the tissue deformation during heating. We could obtain the temperature-dependent ratio change of m values by increasing the ROI size. These results suggest that the selection of a proper ROI size would be significantly important for detecting internal temperature changes by the ratio change of m values because not only the tissue deformation owing to heating but also body motion and pulsating exist under in vivo conditions.