Optimized EPI for fMRI studies of the orbitofrontal cortex
Optimized EPI for fMRI studies of the orbitofrontal cortex
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DOI：
10.1016/s1053-8119(03)00073-9
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发表时间：
2003-06-01
期刊：
影响因子：
5.7
通讯作者：
Turner, R
中科院分区：
文献类型：
--
作者：
Deichmann, R;Gottfried, JA;Turner, R
梯度回波回波平面成像（EPI）中的常见问题是由空气/组织界面附近的磁化率梯度引起的图像失真和信号损失的发生。由于EPI经常用于基于血氧水平依赖效应的功能磁共振成像实验，因此可能会损害对受磁化率梯度影响的某些大脑区域（如颞叶和眶额皮质）的功能研究。在这项工作中，提出了一种方法，在某些区域的眶额皮质的信号恢复。平面内磁化率梯度的影响通过成像切片方向的优化来减小。平面磁化率梯度通过类似于z匀场的中等准备梯度脉冲部分补偿。与文献中提出的用于降低敏感性效应的其他几种技术相比，该方法不影响时间分辨率，因此适用于事件相关研究。(C)2003 Elsevier Science（美国）。All rights reserved.
A common problem in gradient-echo echo planar imaging (EPI) is the occurrence of image distortions and signal losses caused by susceptibility gradients near air/tissue interfaces. Since EPI is frequently used for functional magnetic resonance imaging experiments based on the blood oxygenation level-dependent effect, functional studies of certain brain regions affected by susceptibility gradients, such as the temporal lobes and the orbitofrontal cortex, may be compromised. In this work a method for signal recovery in certain regions of the orbitofrontal cortex is presented. The influence of in-plane susceptibility gradients is reduced by optimization of the imaging slice orientation. Through-plane susceptibility gradients are partly compensated by means of a moderate preparation gradient pulse similar to z-shimming. In contrast to several other techniques proposed in the literature for reducing susceptibility effects, this method does not compromise the temporal resolution and is therefore applicable to event-related studies. (C) 2003 Elsevier Science (USA). All rights reserved.