EPI image reconstruction with correction of distortion and signal losses
EPI image reconstruction with correction of distortion and signal losses
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DOI：
10.1002/jmri.20672
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发表时间：
2006-09-01
影响因子：
4.4
通讯作者：
Ogawa, Seiji
中科院分区：
文献类型：
--
作者：
Liu, Guoxiang;Ogawa, Seiji
目的：推导并实现一种方法，用于校正几何畸变并恢复由磁化率感应磁场梯度（SFG）在回波平面成像（EPI）中具有大静态场不均匀性的区域中引起的磁共振成像（MRI）信号损失。材料和方法：在传统 EPI 方程中添加考虑场不均匀性和 SFG 的因素，该方程是一个简单的傅里叶变换（IT），用于表达 EPI 扫描的实际 k 空间数据。这个“扭曲的EPI”方程的逆计算被用作内核来校正重建过程中的几何扭曲和强度降低。开发了一种逐步 EPI 重建方法来防止复杂的相位展开问题。从标准 EPI k 空间重建了幻像和人脑的一些 EPI 图像。结果：所有图像均使用所提出的多步骤方法重建。几何畸变得到纠正，SFG 引起的 MRI 信号丢失得到恢复。结论：结果表明，应用我们的方法重建 EPI 图像来减少畸变和 MRI 信号丢失是可行的。
Purpose: To derive and implement a method for correcting geometric distortions and recovering magnetic resonance imaging (MRI) signal losses caused by susceptibility-induced magnetic field gradients (SFGs) in regions with large static field inhomogeneities in echo-planar imaging (EPI).Materials and Methods: Factors to account for field inhomogeneities and SFGs were added in a traditional EPI equation that was a simple Fourier transform (IT) for expressing the actual k-space data of an EPI scan. The inverse calculation of this "distorted EPI" equation was used as a kernel to correct geometric distortions and reductions in intensity during reconstruction. A step-by-step EPI reconstruction method was developed to prevent complicated phase unwrapping problems. Some EPI images of phantom and human brains were reconstructed from standard EPI k-spaces.Results: All images were reconstructed using the proposed multistep method. Geometric distortions were corrected and SFG-induced MRI signal losses were recovered.Conclusion: Results suggest that applying our method for reconstructing EPI images to reduce distortions and MRI signal losses is feasible.