E1995. Practical Guide to Approach and Interpret a Fetal MRI
  1. Meng Geng; Cedar Sinai Medical Center
  2. HaiThuy Nguyen ; Children's Hospital Los Angeles
Although ultrasound (US) is the initial modality of choice for in-utero imaging, fetal magnetic resonance imaging (MRI) is an increasingly utilized adjunct to US. MRI provides excellent soft tissue resolution and can overcome certain limitations such as suboptimal fetal position, maternal body habitus, and global assessment of the fetus. It is important for the radiologist to know the common indications for and how to interpret fetal MRIs. In this exhibit, we aim to provide a basic review of the techniques used in imaging acquisition and offer a practical guide to interpret fetal MRI through illustrative cases. Making pertinent findings and accurate diagnosis can facilitate prenatal counseling, guide management and surgical planning, as well as prognosticate to promote the best outcome for the fetus and mother.

Educational Goals / Teaching Points
The objectives of this educational exhibit are to know the common indications for fetal MRI, understand the technical factors related to imaging, and develop an approach to reading fetal MRI, including identification of commonly encountered pathologies. This exhibit is intended for trainees, general and pediatric radiologists, obstetricians, pediatricians.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Fetal MRI is obtained with a 1.5-T superconducting magnet using a phased-array torso surface coil, centered at fetal region of interest (ROI). Images are acquired with the mother in supine or lateral decubitus position. Fast T2-weighted multiplanar MR pulse sequences such as HASTE/SSFSE are acquired with respect to the mom to evaluate situs and fetal anatomy. Additional orthogonal T2WI can be obtained with respect to the fetus at the ROI such as the brain. T1 gradient echo images are helpful for evaluating hemorrhage, fat, and calcifications. Additionally, thyroid, liver and meconium are T1 hyperintense. When approaching a fetal MRI, it is important to first obtain the relevant clinical history and fetal age. It is important to have a checklist as well as a system-based approach for fetal anatomy. Prior to examining the fetus, use the wide field of view to evaluate maternal and extra-fetal structures, and establish fetal presentation and situs which will help with orientation. In this exhibit, we show a case demonstrating multiple abnormalities on MRI, with a constellation of findings that are consistent with Meckel-Gruber syndrome.

In conclusion, MRI is a valuable adjunct imaging modality complementary to ultrasound in evaluation of fetal anatomy and anomalies. Fetal MRI may be unfamiliar to many radiologists, so we have provided a system-approach to reading a fetal MRI. Recognizing abnormal findings can facilitate prenatal counseling and guide appropriate management, especially if fetal surgery is indicated.