Dynamic shimming for multi-slice magnetic resonance imaging
Dynamic shimming for multi-slice magnetic resonance imaging
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DOI：
10.1002/mrm.1910380316
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发表时间：
1997-09-01
影响因子：
3.3
通讯作者：
Spielman, D
中科院分区：
文献类型：
--
作者：
Morrell, G;Spielman, D
在商用GE Signa 1.5-T成像系统上实现了三个脉冲序列的动态振荡。在成像序列之前获取多层场图，并计算每层的线性垫片项和中心频率。在成像扫描过程中，根据当前切片，在每次脉冲序列重复之前设置线性垫片项和中心频率。获取多层场图和计算每个层的垫片项和中心频率在几秒钟内完成。脉冲序列只需要最小的修改，以增加动态振荡能力。结果显示了脂肪饱和自旋回波序列、单次回波-平面梯度-召回回波序列和螺旋采集梯度-召回回波序列。在所有情况下，对每个切片进行优化的垫片电流和中心频率的动态摆振比对整个感兴趣的体积进行恒定垫片电流和单一中心频率优化的效果更好。
Dynamic shimming has been implemented in three pulse sequences on a commercial GE Signa 1.5-T imaging system. Multi-slice field maps are acquired before the imaging sequence, and linear shim terms and center frequencies are calculated for each slice. During the imaging scan, the linear shim terms and center frequency are set before each pulse sequence repetition according to the current slice. Acquisition of multi-slice field maps and calculation of shim terms and center frequency for each slice are accomplished in a matter of seconds. Pulse sequences require only minimal modification to add dynamic shimming capability. Results are shown for a fat saturation spin-echo sequence, a single-shot echo-planar gradient-recalled echo sequence, and a spiral acquisition gradient-recalled echo sequence. In all cases, dynamic shimming with shim currents and center frequency optimized for each slice is shown to give better results than constant shim currents and a single center frequency optimized for the entire volume of interest.