Inflow Artifact Reduction Using an Adaptive Flip-Angle Navigator Restore Pulse for Late Gadolinium Enhancement of the Left Atrium

PURPOSE Late gadolinium enhancement (LGE) of the left atrium is susceptible to artifacts arising from the right pulmonary veins, caused by inflowing blood tagged by the navigator restore pulse. The purpose of this study was to evaluate a new method to reduce the inflow artifact using an adaptive flip-angle restore pulse. METHODS A low-restore angle reduces the inflow artifact but may lead to a poor navigator SNR. The proposed approach aims to determine the patient-specific restore angle, which optimizes the trade-off between inflow artifacts and navigator SNR. Three-dimensional LGE with adaptive navigator restore (3D LGEA ) was implemented by incrementing the flip angle of the restore pulse from a starting value of 0°, based on the navigator normalized cross-correlation. Magnetic resonance imaging experiments were performed on a 1.5T scanner. The value of 3D LGEA was compared with 3D LGE with a constant 180° restore pulse (3D LGE180 ) in 22 patients with heart diseases. The values of 3D LGEA and 3D LGE180 were compared in terms of pulmonary vein blood signal relative to reference blood in the descending aorta (PVrel ) and visual scoring to determine level of motion artifacts using a 4-point scale (1 = severe artifacts; 4 = no artifacts). RESULTS The value of PVrel was significantly lower for 3D LGEA than for 3D LGE180 (1.16 ± 0.23 vs. 1.59 ± 0.29, P < .001). Furthermore, visual scoring of the motion artifacts yielded no difference (P = .78). CONCLUSION Adaptively adjusting the navigator restore flip angle based on the navigator normalized cross-correlation reduces the 3D LGE inflow artifact without affecting image quality or the scan time.