PRENATAL MAGNETIC-RESONANCE-IMAGING ENHANCES FETAL DIAGNOSIS

Background: Ultrasound (US) evaluation of some fetal anomalies provide s limited information. Anatomic details th st affect prognosis and sel ection for fetal therapy, such as liver herniation and pulmonary hypop lasia in congenital diaphragmatic hernia (CDH) and airway patency in g iant neck masses, may be difficult to delineate using conventional son ographic methods. The authors evaluated the utility of prenatal magnet ic resonance imaging (MRI) with new ultrafast imaging sequences in the diagnosis and management of fetal anomalies. Methods: From April 1996 to April 1997 45 MRI scans were performed in 31 pregnant women with a n US diagnosis of a fetal anomaly. The US diagnoses included CDH, gian t neck masses, lung masses, abdominal and pelvic abnormalities, twin a nomalies, and central nervous system (CNS) anomalies. The fetuses rang ed in age from 18 to 39 weeks' gestation (mean, 28.7 weeks). Using a 1 .5-T magnet, a variety of ultrafast imaging sequences were performed i ncluding fast gradient-echo, half-fourier single shot turbo spin-echo (Haste) and echo-planar imaging yielding images with T-1 to T-2 type w eighting. Results: With CDH, MRI demonstrated liver herniation into th e chest in 11 of 14 cases. In four cases, US findings had not been def initive. In two cases of CDH detected by MRI, the primary diagnosis by US had been congenital cystic adenomatoid malformation (CCAM). With l ung masses, MRI accurately distinguished between CCAM and bronchopulmo nary sequestration (BPS). For giant neck masses with potential airway obstruction, MRI scans permitted differentiation of teratoma from cyst ic hygroma and allowed delineation of fetal airway involvement. The ac curate anatomic evaluation facilitated planning for the ex utero intra partum treatment (EXIT) procedure, a technique for securing the airway while the term fetus is still on placental support. With huge abdomin al masses such as enterogenous cyst and lymphangioma, MRI scanning cla rified the diagnosis. Fourteen of the 31 (45%) patients underwent feta I treatment after US and MRI evaluation. Conclusions: Prenatal MRI en hances fetal anatomic evaluation and facilitates perinatal management and family counseling. Ultrafast imaging sequence MRI is helpful to co rroborate and refine US diagnoses. Fetal MRI is a valuable adjunct to US for prenatal diagnosis before fetal surgical intervention for selec ted life-threatening birth defects. Copyright (C) 1998 by W.B. Saunder s Company.