RESUMO
Fetal magnetic resonance imaging (MRI) examinations have become well-established procedures at many institutions and can serve as useful adjuncts to ultrasound (US) exams when diagnostic doubts remain after US. Due to fetal motion, however, fetal MRI exams are challenging and require the MR scanner to be used in a somewhat different mode than that employed for more routine clinical studies. Herein we review the techniques most commonly used, and those that are available, for fetal MRI with an emphasis on the physics of the techniques and how to deploy them to improve success rates for fetal MRI exams. By far the most common technique employed is single-shot T2-weighted imaging due to its excellent tissue contrast and relative immunity to fetal motion. Despite the significant challenges involved, however, many of the other techniques commonly employed in conventional neuro- and body MRI such as T1 and T2*-weighted imaging, diffusion and perfusion weighted imaging, as well as spectroscopic methods remain of interest for fetal MR applications. An effort to understand the strengths and limitations of these basic methods within the context of fetal MRI is made in order to optimize their use and facilitate implementation of technical improvements for the further development of fetal MR imaging, both in acquisition and post-processing strategies.
RESUMO
Cervical teratomas are rare tumors of infancy that are associated with a high mortality rate caused by compression and distortion of the infant's airway. Recent attempts at managing the fetal airway before delivery have focused on the EXIT (ex-utero intrapartum treatment) procedure, in which time to secure an airway is provided while preserving uteroplacental gas exchange. The authors report the use of intraoperative ultrasound guidance during an EXIT procedure for an infant with massive cervical teratoma to aid in identification of the trachea.
