  Purpose: To develop a respiratory-resolved motion-compensation method for
free-breathing, high-resolution coronary magnetic resonance angiography using a
3D cones trajectory.
  Methods: To achieve respiratory-resolved 0.98 mm resolution images in a
clinically relevant scan time, we undersample the imaging data with a
variable-density 3D cones trajectory. For retrospective motion compensation,
translational estimates from 3D image-based navigators (3D iNAVs) are used to
bin the imaging data into four phases from end-expiration to end-inspiration.
To ensure pseudo-random undersampling within each respiratory phase, we devise
a phyllotaxis readout ordering scheme mindful of eddy current artifacts in
steady state free precession imaging. Following binning, residual 3D
translational motion within each phase is computed using the 3D iNAVs and
corrected for in the imaging data. The noise-like aliasing characteristic of
the combined phyllotaxis and cones sampling pattern is leveraged in a
compressed sensing reconstruction with spatial and temporal regularization to
reduce aliasing in each of the respiratory phases.
  Results: In a volunteer and 5 patients, respiratory motion compensation using
the proposed method yields improved image quality compared to
non-respiratory-resolved approaches with no motion correction and with 3D
translational correction. Qualitative assessment by two cardiologists indicates
the superior sharpness of coronary segments reconstructed with the proposed
method (P < 0.01).
  Conclusion: The proposed method better mitigates motion artifacts in
free-breathing, high-resolution coronary angiography exams compared to
translational correction.
