Through time GRAPPA

A non-transitory computer-readable medium storing computer-executable instructions that when executed by a computer control the computer to perform a method, the method comprising:

• controlling a magnetic resonance imaging (MRI) apparatus to acquire, from an object to be imaged, throughout a period of time, a non-Cartesian fully-sampled 3D calibration data set, where different groups in the calibration data set are acquired at different points in time under different gradient encoding conditions produced by an active gradient applied perpendicular to a non-Cartesian encoded plane in the object to be imaged, where the different gradient encoding conditions cause at least three phase encoding differences between consecutive acquisitions;
• controlling the MRI apparatus to acquire an under-sampled non-Cartesian data set from the object to be imaged, where the different gradient encoding conditions produce incoherency between points in the calibration data set and points in the under-sampled non-Cartesian point associated with a moving portion of the object to be imaged;
• and
• controlling the MRI apparatus to reconstruct an image of the object from the under-sampled non-Cartesian data set based, at least in part on a through-time non-Cartesian GRAPPA calibration, where a value for a point missing from k-space in the under-sampled non-Cartesian data set is computed using a GRAPPA weight set calibrated and applied for the missing point, where the GRAPPA weight set is computed from data in two or more different gradient encoding conditions, and where the two or more different gradient encoding conditions are treated as unique calibration time frames as a function of the different gradient encoding conditions.

A magnetic resonance imaging (MRI) apparatus, comprising:

• a first calibration logic that acquires a calibration data set from an object to be imaged, the first calibration logic being configured:
• to control the first and second encoding gradients to define a non-Cartesian encoded plane, to control the third encoding gradient to vary in a direction perpendicular to the non-Cartesian encoded plane in the object to be imaged;
• and to control the MRI apparatus to acquire the calibration data set while the non-Cartesian encoded plane is active and while the third encoding gradient is varying in an amount sufficient to produce three or more differences in the encoding gradient in consecutive acquisitions;
• and
• a second calibration logic that computes a GRAPPA weight set from data in the calibration data set, where data in the calibration data set that was acquired with different third gradients is treated as unique calibration frames.