Method and apparatus for measuring and correcting motion effects using navigator echoes

A method to determine a displacement of an object that is displaced from a reference position comprising the steps of:

• acquiring k space phase data corresponding to a displaced position and the reference position;
• fitting a weighted straight line to the k-space phase data using a least squares minimization;
• and
• determining the displacement from the weighted straight line.

A method to determine a displacement of an object that is rotated, dilated and displaced from a reference position comprising the steps of:

• obtaining k-space magnitude and k-space phase data corresponding to a displaced image space navigator echo and the reference position;
• determining motion parameters due to rotation and dilation from the k-space magnitude data using a weighted least squares minimization;
• and
• determining the displacement for the k-space phase data using the motion parameters and a second weighted least squares minimization.

A method to determine motion parameters of an object comprising the steps of:

• exciting the object using selective volumetric excitation to produce an excited signal;
• obtaining k-space data by sampling the excited signal in k-space using a k-space trajectory sensitized to the motion parameters of the object;
• and
• extracting the motion parameters from the k-space data using a weighted k-space least squares minimization.

A method of detecting coronary artery motion comprising the steps of:

• transmitting a spatial spectral selective pulse to excite epicardial fat to produce an excited signal;
• obtaining k-space data by sampling the excited signal using at least one k-space trajectory;
• and
• extracting motion from the k-space data.