Fast 3D radiofrequency field mapping using echo-planar imaging
Fast 3D radiofrequency field mapping using echo-planar imaging
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DOI：
10.1002/mrm.21083
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发表时间：
2006-12-01
影响因子：
3.3
通讯作者：
Klose, U.
中科院分区：
文献类型：
--
作者：
Jiru, F.;Klose, U.
不均匀的射频(RF)磁场是量化MRI和MRS参数的重要误差来源。为了校正3D数据集中RIF不均匀的影响，有必要了解样本中的3D RF分布。本文提出了一种快速三维射频映射的方法。该方法基于使用回波平面成像(EPI)同时捕获自旋回波(SE)和受激回波(STE)。使用分区和TR=500ms获取3D RIF图需要1.5分钟。通过计算3T时人脑的射频图谱，证明了该序列在活体中的用途。将计算的翻转角与3D刺激回波捕获模式(STEAM)-EPI序列中通过拟合信号行为获得的翻转角进行比较，并分析由于大脑中T-1值的空间相关性而导致的误差，结果表明，人脑中计算的翻转角的精度约为2度。
An inhomogeneous radiofrequency (RF) magnetic field is an essential source of error for the quantification of MRI and MRS parameters. To correct for effects of RIF inhomogeneities in 3D data sets, it is necessary to have knowledge of the 3D RF distribution in the sample. In this paper a method for fast 3D RF mapping is presented. The method is based on the simultaneous acquisition of a spin echo (SE) and a stimulated echo (STE) using echo-planar imaging (EPI). The acquisition of the 3D RIF map using 64 partitions and TR = 500 ms requires 1.5 min. The use of the sequence in vivo is demonstrated by the calculation of the RF maps in the human brain at 3T. The comparison of calculated flip angles with the flip angles obtained by fitting signal behavior in the 3D stimulated-echo acquisition mode (STEAM)-EPI sequence and the analysis of errors due to spatially dependent T-1 values in the brain show that the accuracy of the calculated flip angles in the human brain is about 2 degrees.