While MRI oft the fetal brain mainly requires T2-weighted contrast, the different organs of the rest of the body can be visualized best by using additional sequences, such as T1 –weighted sequences (meconium, fat, liver tissue, glands), echoplanar (EPI) sequences (bones), and diffusion-weighted (DW) sequences (kidneys). Steady-state free precession (SSFP) sequences can be helpful to delineate vascular structures from others within the fetal intrinsic movements of fluid fileld organs (esophagus, bowels), of the whole fetus or of limbs. Then latter may be important in case of spinal abnormalities. Fetal MRI has been found useful in pathologies impairing the lungs. There, lung volumetry, based on T2-weighted imaging helps to predict the respiratory outcome. Therefore MRI is done in most centers in case of (intra) pulmonary lesions, and congenital diaphragmatic hernia respectively. Bowel malformations, such as anal atresia, stenoses, and dislocation (as, for instance, in gastroschisis) can be depicted. Abdominal wall defects that are usually part of complex syndromes can be described in detail, allowing to establish definite diagnoses. Liver pathologies are best recognized using T1- contrast that may be changed, even if the liver has a normal size. Kidneys display pronounced hyperintensity on DWimaging which enables their identification even in unusual places (pelvic kidney..). Even if bone imaging can be done accurately using ultrasound, MRI might be helpful in complex syndromes where bone pathologies may part of, for instance in dysraphism or skeletal dysplasia with associated abnormalities of other structures. Muscle dystrophies are characterized by the presence of fat instead of muscular tissue, which can be seen using T1- weighted images. T1-weighted images are also used to detect the pituitary gland by its hyperintensity and to determine the size of the equally hyperintense thyroid gland. Fetal body MR-imaging has to be done in knowledge of the changing presentation of the organs with respect to gestational age. Not all pathologies may be seen already in the second trimester.

Acknowledgements

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References

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