Fetal-Neonatal Neuroimaging and Developmental Science Center, Boston Children's Hospital, Harvard Medical School, Boston, MA, United States.
Madrid-MIT M+Vision Consortium in RLE, Massachusetts Institute of Technology, Cambridge, MA, United States.
J Magn Reson Imaging. 2017 Aug;46(2):403-412. doi: 10.1002/jmri.25585. Epub 2017 Feb 2.
To present a method for spatiotemporal alignment of in-utero magnetic resonance imaging (MRI) time series acquired during maternal hyperoxia for enabling improved quantitative tracking of blood oxygen level-dependent (BOLD) signal changes that characterize oxygen transport through the placenta to fetal organs.
The proposed pipeline for spatiotemporal alignment of images acquired with a single-shot gradient echo echo-planar imaging includes 1) signal nonuniformity correction, 2) intravolume motion correction based on nonrigid registration, 3) correction of motion and nonrigid deformations across volumes, and 4) detection of the outlier volumes to be discarded from subsequent analysis. BOLD MRI time series collected from 10 pregnant women during 3T scans were analyzed using this pipeline. To assess pipeline performance, signal fluctuations between consecutive timepoints were examined. In addition, volume overlap and distance between manual region of interest (ROI) delineations in a subset of frames and the delineations obtained through propagation of the ROIs from the reference frame were used to quantify alignment accuracy. A previously demonstrated rigid registration approach was used for comparison.
The proposed pipeline improved anatomical alignment of placenta and fetal organs over the state-of-the-art rigid motion correction methods. In particular, unexpected temporal signal fluctuations during the first normoxia period were significantly decreased (P < 0.01) and volume overlap and distance between region boundaries measures were significantly improved (P < 0.01).
The proposed approach to align MRI time series enables more accurate quantitative studies of placental function by improving spatiotemporal alignment across placenta and fetal organs.
1 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:403-412.
提出一种用于在母体高氧条件下采集的胎儿磁共振成像（MRI）时间序列的时空配准方法，以便能够更好地定量跟踪血氧水平依赖（BOLD）信号变化，这些信号变化可以描述氧气通过胎盘向胎儿器官的转运。
用于对单次激发梯度回波回波平面成像采集的图像进行时空配准的流水线包括 1）信号非均匀性校正，2）基于非刚性配准的容积内运动校正，3）跨容积的运动和非刚性变形校正，以及 4）检测要从后续分析中丢弃的异常体积。使用该流水线分析了 10 名孕妇在 3T 扫描期间采集的 BOLD MRI 时间序列。为了评估流水线的性能，检查了连续时间点之间的信号波动。此外，还使用了一部分帧中的手动感兴趣区（ROI）描绘和通过从参考帧传播 ROI 获得的描绘之间的体积重叠和距离来定量对齐精度。使用先前证明的刚性配准方法进行比较。
与最新的刚性运动校正方法相比，所提出的流水线改善了胎盘和胎儿器官的解剖配准。特别是，在第一个正常氧期期间出现的意外的时间信号波动显著减少（P < 0.01），并且体积重叠和区域边界之间的距离测量得到了显著改善（P < 0.01）。
所提出的用于配准 MRI 时间序列的方法通过改善胎盘和胎儿器官之间的时空配准，能够更准确地对胎盘功能进行定量研究。
1 技术功效：阶段 1 J. MAGN. RESON. IMAGING 2017;46:403-412.
