Archive | 2021
Volumetric Fetal Flow Imaging with Magnetic Resonance Imaging
Abstract
Fetal development relies on a complex circulatory\nnetwork and accurately assessing the flow distribution is important for\nunderstanding pathologies and potential therapies. In this paper, we\ndemonstrate a method for volumetric multidimensional imaging of fetal flow with\nmagnetic resonance imaging (MRI). Fetal application of MRI faces several\nchallenges such as small vascular structures, unpredictable motion, and lack of\ntraditional cardiac gating methods. Here, orthogonal multislice stacks are\nacquired with accelerated multidimensional radial phase contrast (PC) MRI. Each\nslice is reconstructed into flow sensitive time-series images (CINEs) with\nretrospective intraslice motion correction and image-based fetal cardiac\ngating. CINEs are then combined into a dynamic 3D volume using slice-to-volume\nreconstruction (SVR) while accounting for interslice spatiotemporal\ncoregistration. Validation of the technique is demonstrated in adult volunteers\nby comparing mean flows from SVR with 4D radial PCMRI with bias and limits of\nagreement being -1.1 ml/s and [-12.5 10.2] ml/s. Feasibility is demonstrated in\nlate gestation fetuses by comparing SVR with 2D Cartesian PCMRI with bias and\nlimits of agreement being -0.9 ml/min/kg and [-39.7 37.8] ml/min/kg for mean\nflows. With SVR, we also demonstrate complex flow pathways (such as parallel\nflow streams in the proximal inferior vena cava, preferential shunting of blood\nfrom the ductus venosus into the left side of the heart, and blood returning\nfrom the brain leaving the heart through the main pulmonary artery) for the\nfirst time in human fetal circulation. This method allows for comprehensive\nevaluation of the fetal circulation and enables future studies of fetal\nphysiology.