Patent ID: 6275720
Filing Date: 2001-08-14
Classification: G01R

Abstract:
A method for producing more accurate absolute positional displacement measurements in a time-efficient manner in navigator echo MR imaging of an object disposed to experience periodic motion, said method comprising the steps of:(a) operating an MR system to acquire a reference navigator echo associated with said object when said object is at a specified reference position;(b) applying an MR sequence to said object to acquire a set of MR image data when said object is selectively displaced from said reference position, said data set including an acquired navigator echo having a specified field of view;(c) applying an inverse Fourier transform to said acquired navigator echo to provide a navigator profile in the frequency domain;(d) truncating the field of view of said navigator profile by applying a truncation window thereto;(e) Fourier transforming said truncated navigator profile to provide a processed navigator echo in the time domain,(f) calculating a difference between linear phase shifts respectively associated with said processed navigator echo and said reference navigator echo;(g) displacing said truncation window by an amount representing said difference of said linear phase shifts, after suitable conversion of said linear phase shifts to its corresponding spatial shift;(h) performing a specified number of iterations of the method steps (d)-(g), the phase shift difference which is determined by a final iteration of said specified number of iterations comprising a final phase shift value; and(i) employing said final phase shift value, after suitable conversion to its corresponding spatial value to determine the displacement of said object from said specified reference position when said MR data set is acquired.