OC09.08: Performance of fetal cardiac MRI: an approach to practice

Fetal expert US is the screening method of choice for routine examination of the heart during pregnancy, but is sometimes limited, e.g. by maternal obesity, polyhydramnios or fetal position. MRI has not been a suitable modality for imaging of the fetal heart in the past, as a number of challenges need to be taken into account. Only recently with the advent of technical innovations that allow for fetal cardiac rhythm monitoring within the MR scanner, fetal retrospective gating became available, but a standardised protocol is currently lacking in literature and clinical practice. This study aims to provide an overview of how to prepare and execute fetal cardiac MRI using retrospective Doppler-US gating in the context of fetal MRI in late gestation in comparison to standardised orientations during an US examination of the fetal heart with corresponding schematic, US and MRI image examples and annotated anatomical structures. After performing plane localisers to capture fetal position in relation to maternal anatomy, a fetal thoracic cine stack in axial orientation is applied to concretise the position and architecture of the fetal heart for further planning. For cardiac sequences, utilization of dynamic CINE balanced gradient echo sequences is proposed with respect to the importance of minimising acquisition time to reduce artifacts. A cine stack of a vertical long axis is planned which in turn can contribute to plan a cine stack of a short axis, followed by a four-chamber-view expanded cranially for assessment of the cardiac anatomy as well as position and configuration of the outflow tracts. This is followed by the acquisition of a cine stack of a three-chamber-view. A standardised protocol is necessarily required to provide comparability between the imaging modalities as well as between centres, to obtain high image quality and to properly evaluate morphology and function of the fetal heart leading to an advanced clinical outcome.