Fetal Magnetic Resonance Imaging (MRI) at low field strengths is an exciting new field in both clinical and research settings. Clinical low field (0.55T) scanners are beneficial for fetal imaging due to their reduced susceptibility-induced artifacts, increased T2* values, and wider bore (widening access for the increasingly obese pregnant population). However, the lack of standard automated image processing tools such as segmentation and reconstruction hampers wider clinical use. In this study, we present the Fetal body Organ T2* RElaxometry at low field STrength (FOREST) pipeline that analyzes ten major fetal body organs. Dynamic multi-echo multi-gradient sequences were acquired and automatically reoriented to a standard plane, reconstructed into a high-resolution volume using deformable slice-to-volume reconstruction, and then automatically segmented into ten major fetal organs. We extensively validated FOREST using an inter-rater quality analysis. We then present fetal T2* body organ growth curves made from 100 control subjects from a wide gestational age range (17–40 gestational weeks) in order to investigate the relationship of T2* with gestational age. The T2* values for all organs except the stomach and spleen were found to have a relationship with gestational age (p<0.05). FOREST is robust to fetal motion, and can be used for both normal and fetuses with pathologies. Low field fetal MRI can be used to perform advanced MRI analysis, and is a viable option for clinical scanning.

中文翻译：

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低场强下胎儿身体器官 T2* 弛豫测量 (FOREST)


低场强胎儿磁共振成像 (MRI) 在临床和研究环境中都是一个令人兴奋的新领域。临床低场 (0.55T) 扫描仪有利于胎儿成像，因为它们减少了磁敏感引起的伪影、增加了 T2* 值和更宽的孔径（扩大了日益肥胖的孕妇群体的使用范围）。然而，缺乏分割和重建等标准自动化图像处理工具阻碍了更广泛的临床应用。在这项研究中，我们提出了胎儿身体器官 T2* RElaxometry 在低场 STrength (FOREST) 管道中分析十个主要胎儿身体器官。获取动态多回波多梯度序列并自动重新定向到标准平面，使用可变形切片到体积重建重建为高分辨率体积，然后自动分割成十个主要胎儿器官。我们使用评估者间质量分析对 FOREST 进行了广泛验证。然后，我们展示了 100 名来自较宽胎龄范围（17-40 孕周）的对照受试者的胎儿 T2* 身体器官生长曲线，以研究 T2* 与胎龄的关系。除胃和脾外，所有器官的 T2* 值均被发现与胎龄有关 (p<0.05)。 FOREST 对胎儿运动具有鲁棒性，可用于正常胎儿和患有病理的胎儿。低场胎儿 MRI 可用于执行高级 MRI 分析，是临床扫描的可行选择。