iMAP Beamforming for High Quality High Frame Rate Imaging

TL;DR

This paper introduces an iterative MAP beamforming method (iMAP) that significantly enhances image contrast in high frame rate ultrasound imaging by statistically modeling signals, outperforming traditional methods with minimal additional computational cost.

Contribution

The paper presents a novel iterative MAP beamformer that exploits statistical signal modeling, improving contrast and speckle preservation in ultrasound imaging with fewer transmissions.

Findings

iMAP achieves contrast comparable to traditional methods with fewer transmissions.

The method outperforms coherence factor and Wiener processing in contrast enhancement.

iMAP maintains speckle pattern integrity better than existing interference suppression techniques.

Abstract

We present a statistical interpretation of beamforming to overcome limitations of standard delay-and-sum (DAS) processing. Both the interference and the signal of interest are viewed as random variables and the distribution of the signal of interest is exploited to maximize the a-posteriori distribution of the aperture signals. In this formulation the beamformer output is a maximum-a-posteriori (MAP) estimator of the signal of interest. We provide a closed form expression for the MAP beamformer and estimate the unknown distribution parameters from the available aperture data using an empirical Bayes approach. We propose a simple scheme that iterates between estimation of distribution parameters and computation of the MAP estimator of the signal of interest, leading to an iterative MAP (iMAP) beamformer. This results in a significant improvement of the contrast compared to DAS without severe increase in computational complexity or need for fine-tuning of parameters. By implementing iMAP on both simulated and experimental data, we show that only 13 transmissions are required to obtain contrast comparable to DAS with 75 plane-waves. The proposed method is compared to other interference suppression techniques such as coherence factor and scaled Wiener processing and shows improved contrast and better preserved speckle pattern.