Exploring the limits of RF shimming for high-field MRI of the human head
Exploring the limits of RF shimming for high-field MRI of the human head
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DOI：
10.1002/mrm.21013
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发表时间：
2006-10-01
影响因子：
3.3
通讯作者：
Collins, Christopher M.
中科院分区：
文献类型：
--
作者：
Mao, Weihua;Smith, Michael B.;Collins, Christopher M.
已经提出了几种方法来克服高场MRI中射频（RF）磁场不均匀性的影响。这些方法中的一些至少部分地依赖于独立地控制发射阵列中的一个多元件RF线圈或不同RF线圈中的不同驱动的幅度和相位的能力。单独调整这些驱动幅度和相位以产生均匀的RF磁场（B-1）被称为RF匀场，并且在每个频率处具有某些限制，如麦克斯韦方程的可能解所指示的。在这里，我们使用数值计算来探索在人体头部的RF匀场的限制。我们发现，16个元件的阵列可以在高达600 MHz的频率下有效地对单个切片进行匀场，并在高达300 MHz的频率下对整个大脑进行匀场，而80个元件的阵列可以在高达600 MHz的频率下对整个大脑进行匀场。
Several methods have been proposed for overcoming the effects of radiofrequency (RF) magnetic field inhomogeneity in high-field MRI. Some of these methods rely at least in part on the ability to independently control magnitude and phase of different drives in either one multielement RF coil or in different RF coils in a transmit array. The adjustment of these drive magnitudes and phases alone to create uniform RF magnetic (B-1) fields has been called RF shimming, and has certain limits at every frequency as dictated by possible solutions to Maxwell's equations. Here we use numerical calculations to explore the limits of RF shimming in the human head. We found that a 16-element array can effectively shim a single slice at frequencies up to 600 MHz and the whole brain at up to 300 MHz, while an 80-element array can shim the whole brain at up to 600 MHz.