Fetal magnetic resonance imaging and ultrasound

Abstract

Magnetic resonance imaging (MRI) has been increasingly adopted in obstetrics practice in the past three decades. MRI aids prenatal ultrasound and improves diagnostic accuracy for selected maternal and fetal conditions. However, it should be considered only when highquality ultrasound cannot provide certain information that affects the counseling, prenatal intervention, pregnancy course, and delivery plan. Major indications of fetal MRI include, but are not restricted to, morbidly adherent placenta, selected cases of fetal brain anomalies, thoracic lesions (especially in severe congenital diaphragmatic hernia), and soft tissue tumors at head and neck regions of the fetus. For fetal anatomy assessment, a 1.5-Tesla machine with a fast T2-weighted single-shot technique is recommended for image requisition of common fetal abnormalities. Individual judgment needs to be applied when considering usage of a 3-Tesla machine. Gadolinium MRI contrast is not recommended during pregnancy. MRI should be avoided in the first half of pregnancy due to small fetal structures and motion artifacts. Assessment of fetal cerebral cortex can be achieved with MRI in the third trimester. MRI is a viable research tool for noninvasive interrogation of the fetus and the placenta.

Imaging in pregnancy

“…23 MRI is useful for assessing a variety of medical conditionsfor example, posterior reversible encephalopathy syndrome, cerebral venous thrombosis, 31 acute appendicitis, 14 Crohn's disease 32 and suspected morbidly adherent placenta. 33 Antenatal MRI is increasingly used to further evaluate structural fetal anomalies, including cranial lesions (ventriculomegaly, agenesis of the corpus callosum, gyral or sulcation pattern), 34 neural tube defects, congenital pulmonary airway malformations, congenital diaphragmatic hernia and cardiovascular anomalies (teratoma, rhabdomyoma or vascular abnormalities). 33 Obstetric MRI can be technically challenging to perform and interpret given the movement of the fetus and variable lie and presentation.…”

“…33 Antenatal MRI is increasingly used to further evaluate structural fetal anomalies, including cranial lesions (ventriculomegaly, agenesis of the corpus callosum, gyral or sulcation pattern), 34 neural tube defects, congenital pulmonary airway malformations, congenital diaphragmatic hernia and cardiovascular anomalies (teratoma, rhabdomyoma or vascular abnormalities). 33 Obstetric MRI can be technically challenging to perform and interpret given the movement of the fetus and variable lie and presentation. However, MRI has several advantages over antenatal ultrasound.…”

Fetal Magnetic Resonance Imaging of Head and Neck Anomalies

“…Based on animal studies, maximum tissue-dependent values have been defined for the thermal index and mechanical index for each examination. [1][2][3] With MRI, there are also potential biological and mechanical risks, including energy deposition, induced currents, and acoustic noise in MRI. Several studies have been performed in animal models and human subjects with regard to the risks of static, pulsed radiofrequency, and timevarying gradient electromagnetic fields.…”

“…Several studies have been performed in animal models and human subjects with regard to the risks of static, pulsed radiofrequency, and timevarying gradient electromagnetic fields. [2][3][4][5][6] In 2014, the Food and Drug Administration defined maximum fetal specific absorption ratio exposure limits of 4 W/kg averaged over 15 minutes in the whole body, and 3.2 W/kg averaged over 10 minutes in the head during any single MRI examination. In addition, slew rates (magnetic field changes) should not exceed 60 T/s.…”

Descripción de la experiencia en RM cerebral fetal en Cali - Colombia

“…El 85% de los casos de ventriculomegalia están asociados a otras alteraciones. Una de las ventajas de la RMF, es la posibilidad de realizar una evaluación anatómica fetal completa en busca de alteraciones relacionadas en otros sistemas [2][3][4][5] .…”