Calibration of gradient propagation delays for accurate two-dimensional radiofrequency pulses
Calibration of gradient propagation delays for accurate two-dimensional radiofrequency pulses
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DOI：
10.1002/mrm.20308
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发表时间：
2005-01-01
影响因子：
3.3
通讯作者：
Jezzard, P
中科院分区：
文献类型：
--
作者：
Davies, NP;Jezzard, P
每个物理轴上梯度波形的请求和实际开始时间之间的硬件相关延迟对于多维选择性激励特别重要，其中梯度和射频（RF）波形的同步至关重要。提出了一种用于梯度传播延迟的精确校准的方法，以优化2D RF脉冲的空间精度，尽管结果也可用于减少其他MR技术中的伪影。利用213个RF脉冲对梯度和RF波形之间的未校正时移的灵敏度来精确校准每个物理梯度轴上的传播延迟。这是使用一种技术实现的，该技术将恒定角速率螺旋k空间轨迹2D RF脉冲的分量波形中的梯度延迟效应与后续激励分布的空间位置相关联。还进行了比较与一个程序的基础上，先前描述的k-空间绘图方法，显示广泛的协议，但与一些差异，说明了多维RF脉冲的自参考校正方法的价值。(C)2004 Wiley-Liss，Inc.
Hardware-related delays between the requested and actual start times of the gradient waveforms on each physical axis are of particular importance for multidimensional selective excitation in which the synchronization of gradient and radiofrequency (RF) waveforms is critical. A method is proposed for the accurate calibration of gradient propagation delays to optimize the spatial accuracy of 2D RF pulses, although the results may also be used to reduce artifacts in other MR techniques. e sensitivity of 213 RF pulses to uncorrected time shifts between the gradient and RF waveforms was exploited to calibrate accurately the propagation delays on each physical gradient axis. This was achieved using a technique that relates the effect of gradient delays in the component waveforms of a constant-angular rate spiral k-space trajectory 2D RF pulse to the spatial location of the subsequent excitation profile. Comparison was also made with a procedure based on a previously described k-space plotting method, showing broad agreement, but with some discrepancies that illustrate the value of a self-referenced correction method for multidimensional RF pulses. (C) 2004 Wiley-Liss, Inc.