Fetal Blood Flow Assessment Using Motion-Robust Whole Heart 4D Cine MRI

Background: Fetal cardiac imaging has a significant impact on patient management and counseling in congenital heart disease (CHD) but encompasses a multitude of challenges, including very small structures encapsulated in the womb, rapid fetal heart rate (140–180/min), unpredictable fetal motion, and maternal respiration. While fetal echocardiography is the gold standard for prenatal diagnosis of structural abnormalities, there are limitations for quantification of fetal blood flow and cardiac function. Volumetric flow assessment by Doppler techniques is susceptible to turbulent flow, cross-sectional area extrapolation and the angle of insonation. Current MRI techniques based on metric-optimized gating or external ultrasound-gating have provided the ability to map the fetal circulation, thus providing important insights into pathophysiology and prognostication in CHD. However, these techniques require precise slice-plane selection during acquisition and are susceptible to motion limiting their wider adoption.

Method: In this single-center prospective study, we applied a novel motion-robust reconstruction framework for 4D magnitude and flow data with full temporal resolved cardiac cycle. Combination of our k-t SENSE accelerated balanced steady-state free precession sequence with continuous stable state 2D acquisition using linear frequency “SWEEP” through multiple noncoplanar stacks allows assessment of anatomy and function in one volumetric dataset with 1.25-mm isotropic resolution. Primary objective was to trial feasibility of 4D cine-flow acquisition during routine clinical fetal CMR scans. Secondary objective was to assess difference in cardiac volumetrics and function in major congenital lesions.

Results: Data were acquired from 59 women carrying a fetus with antenatal diagnosis of CHD and six pregnant controls with current research ethics. Acquisition was <15 minutes (median = 5 stacks). Magnitude and flow reconstruction was available in all cases with at least three and four noncoplanar bSSFP stacks, respectively. Correlation of ventricular stroke volumes with flow measurements in major vessels in a single dataset and comparison of healthy controls to major CHD allows a comprehensive new approach to fetal pathophysiology.

Conclusion: The 4D cine-flow MRI allows antenatal structural and functional assessment of fetal circulation in clinical practice. The addition of further cases could establish physiological values to stratify individual deviations in antenatal CHD.

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Artikel online veröffentlicht:
12. Februar 2022