MoCo + ROVir: Synergy Between Respiratory Motion Compensation and Cardiac Receive Region Focusing for Cardiac MRI.

PURPOSE: To improve cardiac motion representation and reduce artifacts for cardiac- and respiratory-resolved imaging through a synergistic combination of retrospective cardiac phased array RF focusing and rigid respiratory motion compensation (MoCo).

METHODS

We incorporated cardiac receive focusing using region-optimized virtual coils (ROVir) and MoCo into cardiac- and respiratory-resolved low-rank tensor (LRT) reconstruction, hypothesizing that the combination of MoCo + ROVir would prioritize the LRT representation of cardiac motion over respiratory motion. We compared LRT, MoCo-LRT, ROVir-LRT, and the proposed MoCo + ROVir-LRT reconstructions of retrospective data from N = 24 pediatric patients with congenital heart disease (CHD) scanned at 3.0 T using ROCK-MUSIC. Technical evaluation metrics included the proportion of cardiac-to-respiratory motion energy in self-gating lines, cardiac motion priority in the temporal basis, flickering energy, and edge sharpness in end-expiratory cardiac cine. Reconstructed cardiac cines were scored by two expert image readers.

RESULTS

MoCo + ROVir significantly increased the proportion of cardiac-to-respiratory motion energy in self-gating lines (p < 0.001) and prioritized cardiac motion in the temporal basis (p < 0.001). MoCo + ROVir reduced flickering energy in cardiac cine images (p < 0.001), sharpened the liver-lung interface (p < 0.001), and improved flickering-specific scores (p = 0.001). Myocardium-blood pool interface sharpness (p = 0.831), cardiac-specific image scores (p = 0.188), and vascular-specific scores (p = 0.901) were not significantly different. Together, these two techniques allowed 3.7-5.2× faster reconstruction times versus LRT-only.

CONCLUSION

The synergy of MoCo + ROVir successfully prioritized cardiac motion, suppressed respiratory motion, and reduced flickering artifacts, with an added benefit of accelerating reconstruction times. The improved respiratory motion handling may provide an avenue for free-breathing cardiac scans in pediatric patients with CHD.