MRI has been increasingly used for detailed visualization of the fetus in utero as well as pregnancy structures. Yet, the familiarity of radiologists and clinicians with fetal MRI is still limited. This article provides a practical approach to fetal MR imaging. Fetal MRI is an interactive scanning of the moving fetus owed to the use of fast sequences. Single-shot fast spin-echo (SSFSE) T2-weighted imaging is a standard sequence. T1-weighted sequences are primarily used to demonstrate fat, calcification and hemorrhage. Balanced steady-state free-precession (SSFP), are beneficial in demonstrating fetal structures as the heart and vessels. Diffusion weighted imaging (DWI), MR spectroscopy (MRS), and diffusion tensor imaging (DTI) have potential applications in fetal imaging. Knowing the developing fetal MR anatomy is essential to detect abnormalities. MR evaluation of the developing fetal brain should include recognition of the multilayered-appearance of the cerebral parenchyma, knowledge of the timing of sulci appearance, myelination and changes in ventricular size. With advanced gestation, fetal organs as lungs and kidneys show significant changes in volume and T2-signal. Through a systematic approach, the normal anatomy of the developing fetus is shown to contrast with a wide spectrum of fetal disorders. The abnormalities displayed are graded in severity from simple common lesions to more complex rare cases. Complete fetal MRI is fulfilled by careful evaluation of the placenta, umbilical cord and amniotic cavity. Accurate interpretation of fetal MRI can provide valuable information that helps prenatal counseling, facilitate management decisions, guide therapy, and support research studies.

The hypothalamus is susceptible to involvement by a variety of processes, including developmental abnormalities, primary tumors of the central nervous system (CNS), vascular tumors, systemic tumors affecting the CNS, and inflammatory and granulomatous diseases. The hypothalamus may also be involved by lesions arising from surrounding structures such as the pituitary gland. Magnetic resonance (MR) imaging is the modality of choice for evaluating the anatomy and pathologic conditions of the hypothalamus. The MR imaging differential diagnosis depends on accurate anatomic localization and tissue characterization of hypothalamic lesions through the recognition of their signal intensity and contrast material enhancement patterns. Diffusion-weighted imaging and proton MR spectroscopy can be helpful in differentiating among various types of hypothalamic lesions. Key MR imaging features, in addition to the patient's age and clinical findings at presentation, may be helpful in developing the differential diagnosis for lesions involving the hypothalamic region.

OBJECTIVE. The purpose of this study was to evaluate the feasibility of imaging the fetal heart with a balanced steady-state free precession MRI sequence along the body and cardiac axes after inadequate echocardiography.SUBJECTS AND METHODS. After technically inadequate echocardiography, MRI was performed on 20 fetuses (mean gestational age, 24 weeks; range, 18–32 weeks) at risk of congenital heart disease. MRI was attempted along the three fetal body planes (n = 20) and cardiac axes (n = 3) without fetal sedation. The images were analyzed with an anatomic segmental approach. Each feature was classified as well visualized or poorly or not visualized. In each group, the Student's t test was used to assess the relation between visibility of fetal cardiac features and gestational age.RESULTS. Imaging was possible along the fetal body and cardiac axes. In the axial plane, a balanced four-chamber view was obtained in all fetuses, enabling evaluation of heart position, axis, chambers, and interventricular septu...

BACKGROUND AND PURPOSE: JSRD are rare autosomal recessive brain malformations. We hypothesized that MR imaging can assess fetuses at risk for JSRD and might influence their diagnoses. MATERIALS AND METHODS: We prospectively performed cranial MR imaging for 12 fetuses (mean GA, 23 weeks; SD, 3.7) at 25% recurrence risk for JSRD. We correlated prenatal MR imaging findings with postnatal MR imaging and clinical outcome. Retrospectively, we compared posterior fossa measurements of the cases with those of 24 age-matched fetuses with proved normal brain MR imaging. Institutional review board approval and consents were obtained. Statistical methods included a t test and ANCOVA tests. RESULTS: Fetal MR imaging correctly diagnosed 3 cases at 22, 28, and 29 weeks of gestation as JSRD, and 9 cases as normal. In JSRD-affected fetuses, prenatal MR imaging detected narrow pontomesencephalic junction (isthmus) with deepening of the interpeduncular fossa and thick horizontally placed superior cerebellar peduncles (MTS), deformed anteriorly convex floor of the fourth ventricle, and midline cerebellar cleft in place of the hypoplastic vermis. Measurements on axial fetal MR imaging at pontomesencephalic junction, ratio of AP diameters of interpeduncular fossa to midbrain/isthmus, and ratio of the AP to transverse diameters of the fourth ventricle were significantly higher in JSRD-affected fetuses than in nonaffected cases and the control group. CONCLUSIONS: MR imaging can diagnose JSRD in at-risk pregnancies by detecting posterior fossa signs. Measurements at the pontomesencephalic junction may enhance fetal MR imaging accuracy in diagnosing JSRD.