Duong S T M, Phung S L, Bouzerdoum A, Boyd Taylor H G, Puckett A M, Schira M M
School of Electrical, Computer and Telecommunications Engineering, University of Wollongong, Australia.
School of Electrical, Computer and Telecommunications Engineering, University of Wollongong, Australia.
J Neurosci Methods. 2020 Apr 15;336:108625. doi: 10.1016/j.jneumeth.2020.108625. Epub 2020 Feb 13.
Functional magnetic resonance imaging (fMRI) enables non-invasive examination of both the structure and the function of the human brain. The prevalence of high spatial-resolution (sub-millimeter) fMRI has triggered new research on the intra-cortex, such as cortical columns and cortical layers. At present, echo-planar imaging (EPI) is used exclusively to acquire fMRI data; however, susceptibility artifacts are unavoidable. These distortions are especially severe in high spatial-resolution images and can lead to misrepresentation of brain function in fMRI experiments.
This paper presents a new method for correcting susceptibility artifacts by combining a T1-weighted (T) image and inverse phase-encoding (PE) based registration. The latter uses two EPI images acquired using identical sequences but with inverse-PE directions. In the proposed method, the T image is used to regularize the registration, and to select the regularization parameters automatically. The motivation is that the T image is considered to reflect the anatomical structure of the brain.
Our proposed method is evaluated on two sub-millimeter EPI-fMRI datasets, acquired using 3T and 7T scanners. Experiments show that the proposed method provides improved corrections that are well-aligned to the T image.
The proposed method provides more robust and sharper corrections and runs faster compared with two other state-of-the-art inverse-PE based correction methods, i.e. HySCO and TOPUP.
The proposed correction method used the T image as a reference in the inverse-PE registration. Results show its promising performance. Our proposed method is timely, as sub-millimeter fMRI has become increasingly popular.
功能磁共振成像（fMRI）能够对人类大脑的结构和功能进行非侵入性检查。高空间分辨率（亚毫米级）fMRI的普及引发了对皮质内部的新研究，比如皮质柱和皮质层。目前，回波平面成像（EPI）专门用于获取fMRI数据；然而，磁化率伪影是不可避免的。这些失真在高空间分辨率图像中尤为严重，并且可能导致fMRI实验中脑功能的错误呈现。
本文提出了一种通过结合T1加权（T）图像和基于反向相位编码（PE）的配准来校正磁化率伪影的新方法。后者使用两个采用相同序列但PE方向相反的EPI图像。在所提出的方法中，T图像用于规范配准，并自动选择正则化参数。其动机在于T图像被认为能够反映大脑的解剖结构。
我们提出的方法在使用3T和7T扫描仪获取的两个亚毫米级EPI-fMRI数据集中进行了评估。实验表明，所提出的方法提供了改进的校正效果，与T图像很好地对齐。
与其他两种基于反向PE的先进校正方法，即HySCO和TOPUP相比，所提出的方法提供了更稳健、更清晰的校正效果，并且运行速度更快。
所提出的校正方法在反向PE配准中使用T图像作为参考。结果显示了其良好的性能。由于亚毫米级fMRI越来越受欢迎，我们提出的方法很及时。
