Afacan Onur, Estroff Judy A, Yang Edward, Barnewolt Carol E, Connolly Susan A, Parad Richard B, Mulkern Robert V, Warfield Simon K, Gholipour Ali
Department of Radiology, Boston Children's Hospital, Boston, MA.
Harvard Medical School, Boston, MA.
Top Magn Reson Imaging. 2019 Oct;28(5):245-254. doi: 10.1097/RMR.0000000000000219.
Fetal magnetic resonance imaging (MRI) has been gaining increasing interest in both clinical radiology and research. Echoplanar imaging (EPI) offers a unique potential, as it can be used to acquire images very fast. It can be used to freeze motion, or to get multiple images with various contrast mechanisms that allow studying the microstructure and function of the fetal brain and body organs. In this article, we discuss the current clinical and research applications of fetal EPI. This includes T2*-weighted imaging to better identify blood products and vessels, using diffusion-weighted MRI to investigate connections of the developing brain and using functional MRI (fMRI) to identify the functional networks of the developing brain. EPI can also be used as an alternative structural sequence when banding or standing wave artifacts adversely affect the mainstream sequences used routinely in structural fetal MRI. We also discuss the challenges with EPI acquisitions, and potential solutions. As EPI acquisitions are inherently sensitive to susceptibility artifacts, geometric distortions limit the use of high-resolution EPI acquisitions. Also, interslice motion and transmit and receive field inhomogeneities may create significant artifacts in fetal EPI. We conclude by discussing promising research directions to overcome these challenges to improve the use of EPI in clinical and research applications.
胎儿磁共振成像（MRI）在临床放射学和研究领域都越来越受到关注。回波平面成像（EPI）具有独特的潜力，因为它可用于非常快速地获取图像。它可用于冻结运动，或通过各种对比机制获取多幅图像，从而能够研究胎儿大脑和身体器官的微观结构及功能。在本文中，我们将探讨胎儿EPI的当前临床及研究应用。这包括利用T2*加权成像更好地识别血液成分和血管，使用扩散加权MRI研究发育中大脑的连接情况，以及使用功能MRI（fMRI）识别发育中大脑的功能网络。当带状或驻波伪影对胎儿结构MRI中常规使用的主流序列产生不利影响时，EPI还可作为一种替代的结构序列。我们还将讨论EPI采集面临的挑战及潜在解决方案。由于EPI采集对敏感性伪影固有敏感，几何畸变限制了高分辨率EPI采集的使用。此外，层间运动以及发射和接收场的不均匀性可能会在胎儿EPI中产生显著伪影。我们通过讨论有前景的研究方向来结束本文，以克服这些挑战，从而改进EPI在临床和研究应用中的使用。
