Rapid online deep artifact suppression for real-time spiral bSSFP CMR with blipped-CAIPI simultaneous multi-slice imaging at 1.5 T

PURPOSE: Real-time (RT) bSSFP MRI enables fast free-breathing cardiovascular imaging but requires 10-16 slices for functional assessment, resulting in prolonged scan times. Simultaneous multi-slice (SMS) imaging can reduce acquisition time but when combined with non-Cartesian trajectories, it relies on iterative reconstructions that often preclude online use. This study investigates deep artifact suppression to facilitate rapid, online reconstruction of RT-SMS. METHODS: A spiral bSSFP RT sequence with SMS-2 was implemented at 1.5 T. Reconstruction used slice separation in k-space, followed by deep artifact suppression in image space using a 3D U-Net. Ten healthy volunteers were prospectively imaged. RT-SMS image quality and reconstruction time were compared between deep artifact suppression and compressed sensing (CS) reconstructions. Left (LV) and right (RV) ventricular volumes at end-diastole (EDV) and end-systole (ESV) and LV mass (LVM) were compared between RT-SMS with deep artifact suppression and reference-standard breath-hold (BH) imaging. RESULTS: The RT-SMS technique acquired each SMS slice-pair within a single cardiac cycle, reducing the total acquisition by ∼13× compared with BH imaging (15 s vs 3 min 15 s). Total reconstruction for RT-SMS using deep artifact suppression took ∼30 s, compared with 24 min 55 s for compressed sensing. Deep artifact suppression consistently outperformed CS in quantitative and qualitative image quality (p < 0.001). Functional agreement between BH and RT-SMS with deep artifact suppression was good (LVEDV: -7.5 ± 6.8 ml, LVESV: -0.9 ± 4.2 ml, RVEDV: -6.4 ± 8.4 ml, RVESV: 0.2 ± 10.7 ml, LVM: -10.3 ± 11.0 g). CONCLUSION: Online deep artifact suppression reconstruction for RT-SMS bSSFP CMR enables free-breathing short-axis coverage with a substantial reduction in acquisition and reconstruction time while maintaining diagnostic image quality.