Fetal MRI: techniques and protocols.

The development of ultrafast sequences has led to a significant improvement in fetal MRI. Imaging protocols have to be adjusted to the rapidly developing fetal central nervous system (CNS) and to the clinical question. Sequence parameters must be changed to cope with the respective developmental stage, to produce images free from motion artefacts and to provide optimum visualization of the region and focus of interest. In contrast to postnatal studies, every suspect fetal CNS abnormality requires examination of the whole fetus and the extrafetal intrauterine structures including the uterus. This approach covers both aspects of fetal CNS disorders: isolated and complex malformations and cerebral lesions arising from the impaired integrity of the feto-placental unit.