Hybrid two-dimensional navigator correction: A new technique to suppress respiratory-induced physiological noise in multi-shot echo-planar functional MRI
Hybrid two-dimensional navigator correction: A new technique to suppress respiratory-induced physiological noise in multi-shot echo-planar functional MRI
复制标题
DOI：
10.1016/j.neuroimage.2007.09.060
复制
发表时间：
2008-02-01
期刊：
影响因子：
5.7
通讯作者：
Menon, Ravi S.
中科院分区：
文献类型：
--
作者：
Barry, Robert L.;Klassen, L. Martyn;Menon, Ravi S.
功能性磁共振成像（fMRI）中一个令人困扰的生理噪声源是由于正常受试者呼吸导致的大脑磁场的时空调制。使用回波平面成像获取的fMRI数据对这些呼吸引起的频率偏移非常敏感，这会导致图像中出现显著的几何失真。由于这些影响随着主磁场的增强而增大，它们可能抵消使用更高磁场所预期的统计功效的增益。由于对回波平面fMRI现有的导航校正技术的一项研究表明，在抑制呼吸引起的生理噪声方面还可以进一步改进，因此提出了一种新的混合二维（2D）导航器。利用这些诱导频率偏移的缓慢空间变化的先验知识，在k空间中使用±0.5 cm⁻¹之间的空间频率为每次激发构建2D场图。对于多次激发的fMRI实验，我们估计，与一维导航回波校正的最佳性能相比，混合2D导航器校正的改进意味着激活体积增加15%，对于具有高t统计量的区域，最大和平均t统计量分别增加6%和10%，对于由于残留生理噪声污染而具有低t统计量的区域，最大和平均t统计量分别增加71%和56%。（c）2007爱思唯尔公司。保留所有权利。
A troublesome source of physiological noise in functional magnetic resonance imaging (fMRI) is due to the spatio-temporal modulation of the magnetic field in the brain caused by normal subject respiration. fMRI data acquired using echo-planar imaging are very sensitive to these respiratory-induced frequency offsets, which cause significant geometric distortions in images. Because these effects increase with main magnetic field, they can nullify the gains in statistical power expected by the use of higher magnetic fields. As a study of existing navigator correction techniques for echo-planar fMRI has shown that further improvements can be made in the suppression of respiratory-induced physiological noise, a new hybrid two-dimensional (21)) navigator is proposed. Using a priori knowledge of the slow spatial variations of these induced frequency offsets, 2D field maps are constructed for each shot using spatial frequencies between +/- 0.5 cm(-1) in k-space. For multi-shot fMRI experiments, we estimate that the improvement of hybrid 2D navigator correction over the best performance of one-dimensional navigator echo correction translates into a 15% increase in the volume of activation, 6% and 10% increases in the maximum and average t-statistics, respectively, for regions with high t-statistics, and 71% and 56% increases in the maximum and average t-statistics, respectively, in regions with low t-statistics due to contamination by residual physiological noise. (c) 2007 Elsevier Inc. All rights reserved.