A magnetic resonance imaging (MRI) system, comprising a magnetic resonance imaging scanner. The MR scanner comprises a main magnet providing a substantially uniform main magnetic field B0 for a subject under observation, the subject represented by a spatial distribution of magnetizations； a radio frequency (RF) coil system configured to irradiate a plurality of radio frequency (RF) pulses into a region of interest of the subject and to detect a plurality of RF response signals emitted from the region of interest； a gradient coil system configured to provide a perturbation of the main magnetic field B0 using a gradient pulse sequence that causes the RF response signals to encode the spatial distribution of magnetizations in a Fourier domain on a plurality of read-out paths； and a controller in communication with the RF coil system and the gradient coil system to synchronously provide the RF coil system with the plurality of RF pulses and the gradient coil system with the gradient pulse sequence. The gradient pulse sequence comprises a navigator pulse that causes one of the plurality of RF response signals to encode the spatial distribution of magnetizations in the Fourier domain on a pre-determined navigator path that represents a fixed projection of the region of interest of the subject, the pre-determined navigator path is suitable to be in a direction different from directions of the read-out paths, and the fixed projection of the subject is capable of tracking a motion of the subject.
