A method for use in acoustic imaging, comprising: transmitting, from a transmitter, a first sound wave pulse at a first frequency determined by a maximum sampling rate of a receiver; transmitting at least one second sound wave pulse at a frequency substantially equal to the first frequency, the first and at least one second sound wave pulses being transmitted substantially within a fraction of a sample interval of the receiver; receiving and sampling, at the receiver, a reflection of at least two of the first and at least one second pulses to generate a set of receiver samples; and expanding the set of receiver samples, based on the first frequency and a total number of the first and at least one second pulses transmitted, to generate an expanded sample set with a larger number of samples than the set of receiver samples.

Various examples are provided related to estimation of viscoelasticity of an arterial or venous wall. In one example, a method includes obtaining ultrasound data of an arterial or venous wall for a defined acoustic radiation force; and determining viscoelasticity of the arterial or venous wall. The viscoelasticity can be determined based upon correlation between measured and simulated wall velocity of the ultrasound data in a space-time, a wavenumber-frequency, wavenumber-time, or space-frequency domain; or in a sequential manner by determining the elastic part of the modulus by matching measured and simulated phase velocities and determining the viscoelasticity part by matching measured and simulated wall velocities; or a combination of both. The simulated velocity can be determined for a wall thickness and viscoelastic modulus of the arterial or venous wall through full wave analysis. In another example, a system includes an ultrasound scanner and a computing device that can implement the method.