Abstract: The concentration and/or radii of a contrast agent in a fluid can be estimated by acquiring ultrasound spectral data, performing spectral analysis to generate a linear estimation of the power spectrum, and correlating at least one spectral parameter to a predetermined distribution function for the contrast agent. If the mean radius squared of particles is known, then the concentration of contrast agent particles can be calculated. If the concentration is constant, then relative variations in mean radius squared can be determined.

Abstract: The concentration and/or radii of a contrast agent in a fluid can be estimated by acquiring ultrasound spectral data, performing spectral analysis to generate a linear estimation of the power spectrum, and correlating at least one spectral parameter to a predetermined distribution function for the contrast agent. If the mean radius squared of particles is known, then the concentration of contrast agent particles can be calculated. If the concentration is constant, then relative variations in mean radius squared can be determined.

Abstract: Fluid flow rate and perfusion rate are measured using ultrasound techniques by introducing a contrast agent into a fluid stream and then selectively modifying the contrast agent particles within a target area by the application of a focused pulse of relatively low frequency ultrasonic energy, thus creating a zone of reduced backscatter in the target area. The restoration of the zone of reduced backscatter or the movement of the zone of reduced backscatter is monitored, preferably using high frequency ultrasound, to determine the flow rate or perfusion rate of the fluid. Spectral parameters of ultrasound return signals are evaluated to determine an estimate of contrast agent concentration and/or mean particle size.