Motion Estimated and Compensated Compressive Sensing Dynamic MRI Under Field Inhomogeneity

Hong Jung¹, Jaeseok Park², Jong Chul Ye³

Recently, we proposed a compressed sensing dynamic MR technique called k-t FOCUSS that extends the conventional k-t BLAST/SNESE by exploiting the sparsity of x-f signal. Especially, we found that when a fully sampled reference frame is available more sophisticated prediction methods such as RIGR and motion estimation and compensation (ME/MC) can significantly sparsify the residual and improve the overall reconstruction quality. Among these, ME/MC is especially useful since it can be used for arbitrary trajectories such as radial and spiral. However, our extensive experiments with non-cartesian trajectory have demonstrated that there exist technical issues in applying the ME/MC to non-cartesian trajectory due to the field inhomogeneities. This paper showed that if the ME/MC is done in magnitude image domain and the lost phase is compensated from the current frame estimate, the field inhomogeneity problem can be significantly alleviated. Furthermore, we showed that the introduction of half-pel ME/MC and intra block mode within the estimation loop can improve the overall reconstruction quality of compressed sensing dynamic MRI.