INTRODUCTION Fetal cardiovascular magnetic resonance (CMR) imaging is used clinically and for research, but has been previously limited due to lack of direct gating methods. A CMR-compatible Doppler ultrasound (DUS) gating device has resolved this. However, the DUS-gating method is not validated against the current reference method for fetal phase-contrast blood flow measurements, metric optimized gating (MOG). Further, we investigated how different methods for vessel delineation affect flow volumes and observer variability in fetal flow acquisitions. AIMS To 1) validate DUS gating versus MOG for quantifying fetal blood flow; 2) assess repeatability of DUS gating; 3) assess impact of region of interest (ROI) size on flow volume; and 4) compare time-resolved and static delineations for flow volume and observer variability. METHODS Phase-contrast CMR was acquired in the fetal descending aorta (DAo) and umbilical vein by DUS gating and MOG in 22 women with singleton pregnancy in gestational week 360 (265-400) with repeated scans in six fetuses. Impact of ROI size on measured flow was assessed for ROI:s 50-150% of the vessel diameter. Four observers from two centers provided time-resolved and static delineations. Bland-Altman analysis was used to determine agreement between both observers and methods. RESULTS DAo flow was 726 (348-1130) ml/min and umbilical vein flow 366 (150-782) ml/min by DUS gating. Bias±SD for DUS-gating versus MOG were - 45 ± 122 ml/min (-6 ± 15%) for DAo and 19 ± 136 ml/min (2 ± 24%) for umbilical vein flow. Repeated flow measurements in the same fetus showed similar volumes (median CoV = 11% (DAo) and 23% (umbilical vein)). Region of interest 50-150% of vessel diameter yielded flow 35-120%. Bias±SD for time-resolved versus static DUS-gated flow was 33 ± 39 ml/min (4 ± 6%) for DAo and 11 ± 84 ml/min (2 ± 15%) for umbilical vein flow. CONCLUSIONS Quantification of blood flow in the fetal DAo and umbilical vein using DUS-gated phase-contrast CMR is feasible and agrees with the current reference method. Repeatability was generally high for CMR fetal blood flow assessment. An ROI similar to the vessel area or slightly larger is recommended. A static ROI is sufficient for fetal flow quantification using currently available CMR sequences.

中文翻译：

---

使用多普勒超声门控通过心血管磁共振成像对胎儿血流进行量化：针对度量优化门控的验证。

引言 胎儿心血管磁共振 (CMR) 成像用于临床和研究，但之前由于缺乏直接门控方法而受到限制。兼容 CMR 的多普勒超声 (DUS) 门控设备解决了这个问题。然而，DUS 门控方法未针对胎儿相位对比血流测量的当前参考方法、度量优化门控 (MOG) 进行验证。此外，我们研究了血管描绘的不同方法如何影响胎儿流量采集中的流量和观察者变异性。目标 1) 验证 DUS 门控与 MOG 对胎儿血流的量化；2) 评估 DUS 选通的可重复性；3) 评估感兴趣区域 (ROI) 大小对流量的影响；4) 比较流量和观察者可变性的时间分辨和静态描述。方法 通过 DUS 门控和 MOG 在妊娠第 360 周 (265-400) 的 22 名单胎妊娠妇女中获得胎儿降主动脉 (DAo) 和脐静脉的相位对比 CMR，并对 6 个胎儿进行重复扫描。ROI 大小对测量流量的影响被评估为 ROI:s 50-150% 的血管直径。来自两个中心的四名观察员提供了时间分辨和静态描绘。Bland-Altman 分析用于确定观察者和方法之间的一致性。结果通过 DUS 门控，DAo 流量为 726 (348-1130) ml/min，脐静脉流量为 366 (150-782) ml/min。DUS 门控与 MOG 的偏差±SD 为 - DAo 的 45 ± 122 ml/min (-6 ± 15%) 和脐静脉流量的 19 ± 136 ml/min (2 ± 24%)。同一胎儿的重复流量测量显示相似的体积（中位数 CoV = 11% (DAo) 和 23%（脐静脉））。感兴趣的区域 50-150% 的血管直径产生了 35-120% 的流量。时间分辨与静态 DUS 门控流量的偏差±SD 对于 DAo 为 33 ± 39 ml/min (4 ± 6%)，对于脐静脉流量为 11 ± 84 ml/min (2 ± 15%)。结论 使用 DUS 门控相位对比 CMR 对胎儿 DAo 和脐静脉中的血流进行定量是可行的，并且与当前的参考方法一致。CMR 胎儿血流评估的可重复性普遍较高。建议使用与血管面积相似或稍大的 ROI。静态 ROI 足以使用当前可用的 CMR 序列对胎儿流量进行量化。结论 使用 DUS 门控相位对比 CMR 对胎儿 DAo 和脐静脉中的血流进行定量是可行的，并且与当前的参考方法一致。CMR 胎儿血流评估的可重复性普遍较高。建议使用与血管面积相似或稍大的 ROI。静态 ROI 足以使用当前可用的 CMR 序列对胎儿流量进行量化。结论 使用 DUS 门控相位对比 CMR 对胎儿 DAo 和脐静脉中的血流进行定量是可行的，并且与当前的参考方法一致。CMR 胎儿血流评估的可重复性普遍较高。建议使用与血管面积相似或稍大的 ROI。静态 ROI 足以使用当前可用的 CMR 序列对胎儿流量进行量化。