Prenatal ultrasound (US) is the first prenatal imaging tool for screening and evaluation of posterior fossa malformations since it is noninvasive, widely available, and safe for both mother and child. Fetal MRI is a widely used secondary technique to confirm, correct, or complement questionable US findings and plays an essential role in evaluating fetuses with suspected US findings and /or positive family history. The main sequences of fetal MRI consist of T2-weighted (T2w) ultrafast, single-shot sequences. Axial, coronal, and sagittal images are typically acquired allowing for a detailed evaluation of the posterior fossa contents. Also, various complimentary sequences, such as T1w, T2*w gradient sequences, or advanced techniques, including diffusion-weighted imaging, diffusion tensor imaging, and magnetic resonance spectroscopy, may provide additional information based on the studied malformation. Inclusion of these techniques should be done with careful risk–benefit analysis. The use of fetal MRI also aims to evaluate for associated anomalies. In addition, prenatal diagnosis of posterior fossa malformations is still a challenge but advances in knowledge in human developmental anatomy, genetic, and imaging recognition patterns have enabled us to shed some light on prognostic information that will help with the counseling of families. Finally, high-resolution late third trimester fetal MRI offers a safe alternative to early postnatal MR imaging, basically taking advantage of the uterine environment as a kind of “maternal incubator.” Our goal is to discuss the spectrum of prenatal posterior fossa pathologies that can be studied by fetal MRI and their key neuroimaging features.

中文翻译：

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后颅窝异常的胎儿 MRI 评估：综述

产前超声 (US) 是第一个用于筛查和评估后颅窝畸形的产前成像工具，因为它是非侵入性的、可广泛使用且对母婴安全的。胎儿 MRI 是一种广泛使用的辅助技术，用于确认、纠正或补充可疑的超声检查结果，并在评估超声检查结果和/或阳性家族史的胎儿中发挥重要作用。胎儿 MRI 的主要序列由 T2 加权 (T2w) 超快单次序列组成。通常采集轴向、冠状和矢状图像，以便对后颅窝内容物进行详细评估。此外，各种互补序列，例如 T1w、T2*w 梯度序列，或先进技术，包括扩散加权成像、扩散张量成像和磁共振波谱，可以根据所研究的畸形提供额外的信息。应通过仔细的风险收益分析来纳入这些技术。胎儿 MRI 的使用还旨在评估相关异常。此外，后颅窝畸形的产前诊断仍然是一项挑战，但人类发育解剖学、遗传和影像识别模式知识的进步使我们能够了解有助于家庭咨询的预后信息。最后，高分辨率晚期晚期胎儿 MRI 提供了一种替代产后早期 MR 成像的安全替代方法，基本上利用子宫环境作为一种“母体孵化器”。