Shaping and Timing Gradient Pulses to Reduce MRI Acoustic Noise
Shaping and Timing Gradient Pulses to Reduce MRI Acoustic Noise
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DOI：
10.1002/mrm.22366
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发表时间：
2010-08-01
影响因子：
3.3
通讯作者：
Hoogduin, Johannes M.
中科院分区：
文献类型：
--
作者：
Segbers, Marcel;Sierra, Carlos V. Rizzo;Hoogduin, Johannes M.
最近提出了一种降低MRI中梯度系统产生的声学噪声的方法，这种方法基于线性响应理论。由于MRI声学噪声的物理原因是梯度电流的时间导数，因此常见的梯形电流形状主要在上升沿和下降沿期间产生声学梯度线圈响应。在下降沿中，线圈声学响应与上升沿相比呈现180度相位差。因此，通过改变梯形的宽度并保持斜坡恒定，可以抑制一个选定的频率及其高次谐波。该值与梯度线圈系统的主要谐振频率之一匹配。消除单个频率的想法被扩展到第二频率，使用以选定的间隔呈现的两个连续的椭圆形脉冲。两个梯形形状和一个单一的脉冲形状，分别发现6和10分贝的整体声压级降低。声学优化的脉冲形状建议另外测试在一个模拟的回波平面成像读出列车，获得最好的情况下，12分贝的声压级降低。Magn Reson Med 64：546-553，2010. (C)2010 Wiley-Liss，Inc.
A method to reduce the acoustic noise generated by gradient systems in MRI has been recently proposed; such a method is based on the linear response theory. Since the physical cause of MRI acoustic noise is the time derivative of the gradient current, a common trapezoid current shape produces an acoustic gradient coil response mainly during the rising and falling edge. In the falling edge, the coil acoustic response presents a 180 degrees phase difference compared to the rising edge. Therefore, by varying the width of the trapezoid and keeping the ramps constant, it is possible to suppress one selected frequency and its higher harmonics. This value is matched to one of the prominent resonance frequencies of the gradient coil system. The idea of cancelling a single frequency is extended to a second frequency, using two successive trapezoid-shaped pulses presented at a selected interval. Overall sound pressure level reduction of 6 and 10 dB is found for the two trapezoid shapes and a single pulse shape, respectively. The acoustically optimized pulse shape proposed is additionally tested in a simulated echo planar imaging readout train, obtaining a sound pressure level reduction of 12 dB for the best case. Magn Reson Med 64:546-553, 2010. (C) 2010 Wiley-Liss, Inc.