Fetal cardiac cine imaging using highly accelerated dynamic MRI with retrospective motion correction and outlier rejection

Purpose: Development of a MRI acquisition and reconstruction strategy to depict fetal cardiac anatomy in the presence of maternal and fetal motion. 
Methods: The proposed strategy involves (i) acquisition and reconstruction of highly-accelerated dynamic MRI, followed by image-based (ii) cardiac synchronisation, (iii) motion correction, and (iv) outlier rejection, and finally (v) cardiac cine reconstruction. Post-processing was entirely automated aside from a user-defined region of interest delineating the fetal heart. The method was evaluated in thirty mid- to late-gestational age singleton pregnancies scanned without maternal breath-hold. 
Results: The combination of complementary acquisition/reconstruction and correction/rejection steps in the pipeline served to improve the quality of the reconstructed 2D cine images, resulting in increased visibility of small, dynamic anatomical features. Artefact-free cine images were successfully produced in 36/39 acquired data sets; prolonged general fetal movements precluded processing of the remaining three. 
Conclusions: The proposed method shows promise as a motion-tolerant framework to enable further detail in MRI studies of the fetal heart and great vessels. Processing data in image-space allowed for spatial and temporal operations to be applied to the fetal heart in isolation, separate from extraneous changes elsewhere in the field of view. 
Keywords: Magnetic Resonance Imaging; Fetal Heart; Cardiac Cine; Motion Correction; Congenital Heart Disease;