A real-time clinical ultrasound contrast dosimeter with adaptive algorithms

Recent advances in ultrasound technology and contrast agents allow the detection of blood flow at the level of microcirculation. However, information about the concentration of contrast bubbles that is present in systemic blood is rarely available in in-vivo studies. Real-time and quantitative information on contrast bubble performances also is needed for the estimation of blood flow rate and relative vascular volume. In this paper we describe a stand-alone system that provides real-time quantitative measurement of contrast agent concentration in arterial blood. We have developed some adaptive algorithms in this system to perform post-filtering, noise power estimation, power compensation, self-soft thresholding, and waveform smoothing. These algorithms adaptively reduce noise and enhance the Doppler signal in a low signal-to-noise ratio environment, thus allowing reliable measurements of Doppler signal power, mean frequency, and mean intensity. The algorithms have been successfully tested with both simulated noisy Doppler signals and in-vivo measurements using animals.