Following the flow: in vivo imaging of fetal foramen ovale physiology using four-dimensional flow magnetic resonance imaging with doppler ultrasound gating.

The foramen ovale (FO) is a vital conduit of the fetal circulation, directing oxygenated blood from the placenta through the right atrium to the left atrium and thus to the brain and viscera. Due to technical limitations, quantification of flow across the foramen ovale is typically estimated using indirect measurements of prenatal echocardiography. We present a case of a healthy human fetus at 32 weeks of gestation, visualized via Doppler ultrasound-gated 4D flow MRI. Caval blood flow through the foramen ovale was distinctly observed and delineated without using contrast agents, anesthesia, or advanced acquisition/reconstruction methods. This example emphasizes the ability of fetal cardiac MR with 4D flow to demonstrate and potentially quantify the normal physiology of the foramen ovale.