Iterative method for reducing errors in navigator echo mr imaging

Abstract

A method is disclosed for providing a time efficient and accurate measure of the absolute positional displacements of a reference structure in navigator echo MR imaging. The method comprises the steps of operating an MR system to acquire a reference navigator echo associated with the object at a specified reference position, and applying an MR sequence to the object to acquire a set of MR image data when the object is selectively displaced from the reference position. The data set includes an acquired navigator echo having a specified field of view. The method further comprises truncating the acquired navigator echo by means of a selectively positioned truncation window, calculating the difference between linear phase shifts respectively associated with acquired and reference navigator echoes, and displacing the truncation window by an amount representing or corresponding to the phase shift difference in spatial units. Thereupon, the truncating, difference calculation, and truncation window displacement steps are iteratively repeated a specified number of times or when the calculated displacements converge to zero, to provide a final phase shift difference value and an absolute spatial displacement of a reference structure. The final value is used to determine the displacement of the object from the specified reference position when the MR data set is acquired.