Volumetric Reconstruction Resolves Off-Resonance Artifacts in Static and
  Dynamic PROPELLER MRI
Annesha Ghosh Gordon Wetzstein Mert Pilanci Sara Fridovich-Keil
Off-resonance artifacts in magnetic resonance imaging (MRI) are visual
distortions that occur when the actual resonant frequencies of spins within the
imaging volume differ from the expected frequencies used to encode spatial
information. These discrepancies can be caused by a variety of factors,
including magnetic field inhomogeneities, chemical shifts, or susceptibility
differences within the tissues. Such artifacts can manifest as blurring,
ghosting, or misregistration of the reconstructed image, and they often
compromise its diagnostic quality. We propose to resolve these artifacts by
lifting the 2D MRI reconstruction problem to 3D, introducing an additional
"spectral" dimension to model this off-resonance. Our approach is inspired by
recent progress in modeling radiance fields, and is capable of reconstructing
both static and dynamic MR images as well as separating fat and water, which is
of independent clinical interest. We demonstrate our approach in the context of
PROPELLER (Periodically Rotated Overlapping ParallEL Lines with Enhanced
Reconstruction) MRI acquisitions, which are popular for their robustness to
motion artifacts. Our method operates in a few minutes on a single GPU, and to
our knowledge is the first to correct for chemical shift in gradient echo
PROPELLER MRI reconstruction without additional measurements or pretraining
data.