A fourth gradient to overcome slice dependent phase effects of voxel-sized coils in planar arrays.
A fourth gradient to overcome slice dependent phase effects of voxel-sized coils in planar arrays.
复制标题
第四个梯度，用于克服平面阵列中体素大小线圈的切片相关相位效应。
DOI：
10.1109/iembs.2010.5627152
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
Wright,StevenM
中科院分区：
文献类型：
--
作者：
Bosshard,JohnC;Eigenbrodt,EdwinP;McDougall,MaryP;Wright,StevenM
当体素尺寸具有与线圈尺寸相当的尺寸时，来自用于MRI的密集间隔的长且窄的接收线圈的阵列的信号是复杂的。RF线圈在每个体素上产生相位梯度，这取决于与线圈的距离，导致k空间的切片相关移位。第四个梯度线圈已经实现，并与系统的梯度设置一起使用，以创建随切片变化的梯度场。这些梯度一起被脉冲化，以赋予切片相关相位梯度，从而补偿由于RF线圈而导致的切片相关相位。然而，产生期望的切片依赖性的第四梯度中的非线性也导致通过切片的相位斜坡，其干扰正常的切片重聚焦并且导致附加的信号消除和减小的视场。本文讨论了使用第四个梯度线圈补偿RF线圈相位的优点和局限性。
The signals from an array of densely spaced long and narrow receive coils for MRI are complicated when the voxel size is of comparable dimension to the coil size. The RF coil causes a phase gradient across each voxel, which is dependent on the distance from the coil, resulting in a slice dependent shift of k-space. A fourth gradient coil has been implemented and used with the system's gradient set to create a gradient field which varies with slice. The gradients are pulsed together to impart a slice dependent phase gradient to compensate for the slice dependent phase due to the RF coils. However the non-linearity in the fourth gradient which creates the desired slice dependency also results in a through-slice phase ramp, which disturbs normal slice refocusing and leads to additional signal cancelation and reduced field of view. This paper discusses the benefits and limitations of using a fourth gradient coil to compensate for the phase due to RF coils.