Reducing respiratory artifacts in chest MR images through hybrid space motion tracking and postprocessing

A new postprocessing method of correcting for respiratory motion induced artifacts in MRI is presented. The motion of the chest during respiration is modeled as a combination of translation and dilation. Displacements of the chest wall are tracked via a thin, MR-sensitive plate placed on the patient's chest during a scan. Scanning with phase encoding left/right (L/R) and frequency encoding anterior/posterior (A/P) causes the motion artifacts to be repeated in the L/R direction, thus not overlapping on the plate. By performing the inverse A/P Fourier transform, the resulting hybrid space data has A/P spatial data and L/R spatial frequency data, in which the motion of the plate is clearly visible as a nearly periodic waveform. Modeling the motion of the chest wall as an equal combination of translation and dilation allows corrections to the image to be make in k- space using properties of the Fourier transform and the measured displacement data. Noticeable reduction of the intensity of the motion artifacts is achieved, indicating the validity of the motion model and tracking method.