Single-shot fast spin-echo MR imaging of the fetus: a pictorial essay

Ultrasonography (US) is the modality of choice for prenatal screening, but occasionally additional imaging information is needed. Magnetic resonance (MR) imaging is an attractive alternative but until recently has been limited by motion artifact. Single-shot fast spin-echo MR imaging was used to depict normal and abnormal anatomy in 26 fetuses. Thirteen studies were performed for maternal indications and 13 were performed to evaluate fetal abnormalities identified or suspected at US. Three of the fetal abnormalities involved the central nervous system (CNS) and 10 involved other anatomic sites. Results were correlated with findings at postnatal clinical examination, imaging, and pathologic analysis. MR imaging demonstrated normal fetal anatomy without substantial motion artifact. CNS structures were well visualized as early as 18-20 weeks gestation, as were most other normal anatomic structures except the heart. MR imaging also allowed characterization of a variety of abnormalities of the CNS (Arnold-Chiari malformation, Walker-Warburg syndrome, amniotic band syndrome) as well as of other structures (renal agenesis, multicystic dysplastic kidney, abdominal masses, severe limb-body wall defect, clubfoot with arthrogryposis, diaphragmatic hernia). US findings were confirmed in most cases, and additional information about the precise diagnosis or the severity or location of the anomaly often helped guide clinical management. Single-shot fast spin-echo MR imaging of the fetus is a useful adjunct to US in difficult diagnostic situations.