B1-based specific energy absorption rate determination for nonquadrature radiofrequency excitation
B1-based specific energy absorption rate determination for nonquadrature radiofrequency excitation
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DOI：
10.1002/mrm.24215
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发表时间：
2012-11-01
影响因子：
3.3
通讯作者：
Voigt, Tobias
中科院分区：
文献类型：
--
作者：
Katscher, Ulrich;Findeklee, Christian;Voigt, Tobias
目前估计MRI局部和全局比能量吸收率的黄金标准涉及对患者和发射射频线圈进行数值建模。最近，提出了一种患者个体方法，该方法从单独测量的B1图估计比能量吸收率。然而，由于难以区分射频发射和接收的相位贡献，这种方法仅限于正交体积线圈。在这项研究中，分离这两个相位的贡献，通过比较从并行射频传输系统的不同发射通道重建的电导率的方法。这使得特定的能量吸收率估计不仅正交激励，但也为非正交激励的发射阵列的单个元件。虽然不同相位的贡献是已知的，但未知的磁场分量和组织边界伪影限制了该技术。然而，在这项研究中发现的模拟和实验结果之间的高度一致性是有希望的。基于B1的比能量吸收率确定可能会在患者个体的基础上进行任意射频激发。Magn Reson Med，2012年。(c)2012 Wiley Periodicals，Inc.
The current gold standard to estimate local and global specific energy absorption rate for MRI involves numerically modeling the patient and the transmit radiofrequency coil. Recently, a patient-individual method was presented, which estimated specific energy absorption rate from individually measured B1 maps. This method, however, was restricted to quadrature volume coils due to difficulties distinguishing phase contributions from radiofrequency transmission and reception. In this study, a method separating these two phase contributions by comparing the electric conductivity reconstructed from different transmit channels of a parallel radiofrequency transmission system is presented. This enables specific energy absorption rate estimation not only for quadrature excitation but also for the nonquadrature excitation of the single elements of the transmit array. Though the contributions of the different phases are known, unknown magnetic field components and tissue boundary artifacts limit the technique. Nevertheless, the high agreement between simulated and experimental results found in this study is promising. B1-based specific energy absorption rate determination might become possible for arbitrary radiofrequency excitation on a patient-individual basis. Magn Reson Med, 2012. (c) 2012 Wiley Periodicals, Inc.