ICG JKU Linz Lab Talk: 'Efficient motion compensation for fetal MRI'

The recent advent of T2-weighted single shot fast spin echo sequences has enabled magnetic resonance imaging to play an essential role in fetal diagnosis, in particular where ultrasound fails to provide sufficient information to diagnose specific prenatal conditions. Fetal MRI is able to provide good contrast for individual fetal structures such as brain, lung, kidney and liver, and pregnancy related anatomy such as placenta, umbilical cord and amniotic sac.

MRI is considered to be safe after the first trimester for 1.5T and 3T without the use of contrast agents, which may have teratogenic effects. Sedation is not used during a scan and fetuses move freely while the mother breathes normally. Individual ssFSE slices can be acquired fast enough to freeze motion in time, however, motion between slices are likely to corrupt 3D scans by reducing image quality, hiding pathology and causing an overlap between different anatomical regions. ssFSE allows to acquire high resolution `in-plane' slices from the uterus with large field of view and good tissue contrast. However, there are still inter-slice artifacts in the `out-of-plane' views, which consequently limit reliable diagnostics to individual slices.

Slice-to-volume registration techniques and super-resolution image reconstruction methods can be applied to compensate for 3D motion artefacts between single slices. This is currently enabled by oversampling the target input space with multiple orthogonal stacks of 2D slices. Oversampling a target volume with multiple orthogonal stacks of 2D slices allows to apply slice-to-volume registration techniques and super-resolution methods.