Nonlinear characterization of tissue and microbubbles using Nakagami statistical model

The objective of this study is to exploit the statistical signatures of biological tissues and contrast microbubbles in order to develop new strategies for contrast imaging and tissue characterization. For this purpose, the Nakagami statistical model was chosen, because it is more general and simpler to apply than other statistical models to describe the linear and nonlinear ultrasonic echoes of both contrast microbubbles and tissues. Experiments were performed using a 2.5 MHz linear array connected to an open research platform. A commercially phantom was used to mimic tissue and microbubbles backscatters. For several regions of interest and for different microbbubles concentration, the RF signals have been generated at 3 and 5 transmit cycles. The received echoes have been filtered around the center frequency (fundamental) and around twice the center frequency (2nd harmonic). Obtained signals have been analyzed in order to evaluate Nakagami parameter (m), the scaling parameter (0) and the probability density function of the envelopes of the echo signals. These results would be used for improving the quality of images obtained by harmonic imagery.