title: Maximum-likelihood approach to strain imaging using ultrasound
abstract: A maximum-likelihood (ML) strategy for strain estimation is presented as a framework for designing and evaluating bioelasticity imaging systems. Concepts from continuum mechanics, signal analysis, and acoustic scattering are combined to develop a mathematical model of the ultrasonic waveforms used to form strain images. The model includes three-dimensional (3-D) object motion described by affine transformations, Rayleigh scattering from random media, and 3-D system response functions. The likelihood function for these waveforms is derived to express the Fisher information matrix and variance bounds for displacement and strain estimation. The ML estimator is a generalized cross correlator for pre- and post-compression echo waveforms that is realized by waveform warping and filtering prior to cross correlation and peak detection. Experiments involving soft tissuelike media show the ML estimator approaches the Cramer-Rao error bound for small scaling deformations: at 5 MHz and 1.2% compression, the predicted lower bound for displacement errors is 4.4 microns and the measured standard deviation is 5.7 microns.
authors.affiliation: Department of Radiology, University of Kansas Medical Center, Kansas City 66160-7234, USA. mfinsana@ucdavis.edu
authors.initials: MF
authors.lastname: Insana
authors.initials: LT
authors.lastname: Cook
authors.initials: M
authors.lastname: Bilgen
authors.initials: P
authors.lastname: Chaturvedi
authors.initials: Y
authors.lastname: Zhu