Spatial resolution in elasticity imaging

Thus far, spatial resolution in elasticity imaging has been addressed empirically. No clear analytical approaches have emerged because the estimators are nonlinear in the data and signals are time-variant and nonstationary. This paper describes a linear systems approach based on a small-strain impulse approximation that results in the derivation of a local impulse response (LIR) and modulation transfer function (MTF). Closed-form solutions for the strain LIR provide new insights with respect to the effects of instrumentation on axial resolution for strain imaging. Phantom measurements are used to validate results. We found that the correlation window determines axial resolution in most practical situations but that the same system properties that determine B-mode resolution ultimately limit elasticity imaging.