Fetal XCMR

Fetal XCMR (Fetal extended Cardiac-Torso cardiovascular magnetic resonance imaging) is an open-source simulation to advance the development and validation of new fetal cardiovascular magnetic resonance (CMR) techniques. This tool addresses the significant challenge of validating fetal CMR methods due to the unpredictability of fetal movement, which typically prevents repeat measurements. Traditionally, the development of fetal CMR techniques has relied on physical phantoms or postnatal volunteers due to these constraints.

Fetal XCMR uniquely caters to the dynamic physiology of the fetal heart and body, building upon established methods for simulating CMR acquisitions. This simulation creates detailed maternal and fetal anatomy, incorporating simulated motion to represent in vivo conditions accurately. The anatomical models are then mapped to CMR contrast and converted into CMR data, closely mimicking real fetal CMR imaging scenarios.

The validation of Fetal XCMR involved comparing simulated acquisitions with actual fetal CMR images obtained from pregnant women. These comparisons were made using typical scan parameters, with adjustments for motion and noise levels to ensure accuracy. The framework allows for three types of image reconstructions—static, real-time, and CINE—and employs two motion estimation methods (translational motion and fetal heart rate) across various planes of the fetal heart. These simulations demonstrated a high degree of similarity to in-utero acquisitions, validating the feasibility and reliability of the Fetal XCMR framework.

Results from using Fetal XCMR showed that the simulated images closely match the contrast, morphologies, and relative proportions of maternal and fetal anatomy seen in static in-utero images. Moreover, the simulation effectively replicates the visualization of maternal respiratory and fetal cardiac motion in real-time in-utero images. CINE image reconstructions from the simulation also provided excellent delineation of fetal cardiac anatomy and its temporal dynamics, mirroring the quality and detail of actual fetal CMR data.