The usefulness of fetal MRI for prenatal diagnosis

Abstract

Purpose: Fast MRI has provided detailed and reproducible fetal anatomy. This study was performed to evaluate the usefulness of fetal MRI for prenatal diagnosis.

Materials and methods: Fifty-six fetuses with congenital abnormalities on ultrasonography were evaluated by fetal MRI from 2001 to 2004 in Severance Hospital. Final diagnosis was made by postnatal pathology, postnatal MRI, and other modalities (such as ultrasound, retrograde pyelogram). A 1.5-Tesla superconductive MR imaging unit was used to obtain half-Fourier acquisition single-shot turbo spin images.

Results: Of the 56 fetuses, intracranial abnormalities were found in 26 fetuses, intraabdominal abnormalities in 17 fetuses, intrathoracic in 6 fetuses, head and neck in 5 fetuses, and other sites in 2 fetuses. There were six cases in which the diagnoses of fetal MRI and ultrasonography differed. In such cases, fetal MRI provided more exact diagnosis than ultrasonography (5 vs. 0). Three fetuses with intracranial abnormalities on ultrasonography were diagnosed as normal by fetal MRI and in postnatal diagnosis.

Conclusion: Although ultrasonography is known as a screening modality of choice in the evaluation of fetus because of the cost-effectiveness and safety, the sonographic findings are occasionally inconclusive or insufficient for choosing the proper management. Thus, in this study, we suggest that fetal MRI is more useful than ultrasonography for the evaluation of intracranial abnormalities in some instances. For prenatal counseling and postnatal treatment planning, fetal MRI can be informative when prenatal ultrasonography is inadequate and doubtful.

Fig. 1

Number of cases according to affected organ. ^*Soft tissue mass in right leg, sacrococcygeal teratoma.

Fig. 2

Agenesis of corpus callosum in a fetus at 24 weeks' gestation. (A) Arachnoid cyst (arrow head) was suggested in axial sonogram. There was neither ventriculomegaly nor a tear-drop sign in sonographic findings. But, sagittal (B) and coronal (C) magnetic resonance images clearly demonstrated a lack of normal connecting white matter fiber.

Fig. 3

A case diagnosed as suspicious of Dandy-Walker variant by ultrasonography at 26 weeks' gestation due to mild ventricular enlargement (A) and enlarged cisterna magna (B). Transaxial magnetic resonance image shows direct communication between the 4th ventricle and cisterna magna (C) and sagittal magnetic resonance image shows enlarged posterior fossa (D). This case was diagnosed as Dandy-Walker malformation by fetal MRI.

Fig. 4

A case diagnosed as suspicious of fetal ovarian cyst or meconium pseudocyst by ultrasonography at 24 weeks' gestation. A. Coronal sonogram demonstrates well defined heterogeneous echogenic round mass in the fetal abdomen. B. Axial sonogram shows a dilated fetal small bowel. Same patient at 26 weeks' gestation, T2-W sequence (C) and T1-W sequence (D). C. Sagittal scan shows well defined large cystic structure (arrow head) and dilated bowel loops (arrow) with same intermediate signal. (Bl; urinary bladder, S; stomach) D. Coronal scan shows dilated loops with meconium-like signal (black arrows). This case was diagnosed as small bowel obstruction with meconium pseudocyst in fetal MRI and later confirmed as jejunal atresia with meconium pseudocyst by postnatal pathology.