Cassidy P J, Grieve S, Clarke K, Edwards D J
British Heart Foundation Molecular Cardiology Group, Department of Biochemistry, University of Oxford, South Parks Road, OX1 3QU, Oxford, UK.
MAGMA. 2002 Mar;14(1):20-9. doi: 10.1007/BF02668183.
The Transmission-Line Modelling (TLM) method is applied to the electromagnetic characterisation of RF coils and samples for magnetic resonance imaging MRI. Theoretical verification was performed using a simple surface coil. Experimental verification was performed using Alderman-Grant and birdcage coils constructed for use on a 7 T micro-imaging system. The modelling method enabled electromagnetic characteristics of frequency response, electromagnetic field generation, energy stored and power loss to be determined. From these parameters, coil resonant modes, B1 field profiles, voltages, currents, quality factor (Q), pi/2 pulse length, and the equivalent lumped-element circuit components of resistance, inductance and capacitance were calculated. Equations are presented that enable a comprehensive electromagnetic characterisation of the RF coil and sample to be achieved based on the results of the TLM simulations. The use of the TLM method is extended to include the design of safe arbitrary multi-nuclear pulse sequences such that the specific absorption rate (SAR) of tissue, and RF coil component safety limits are not exceeded.
传输线建模（TLM）方法被应用于磁共振成像（MRI）中射频线圈和样品的电磁特性表征。使用一个简单的表面线圈进行了理论验证。使用为7T微型成像系统构建的奥尔德曼 - 格兰特线圈和鸟笼线圈进行了实验验证。该建模方法能够确定频率响应、电磁场产生、储能和功率损耗等电磁特性。根据这些参数，计算了线圈谐振模式、B1场分布、电压、电流、品质因数（Q）、π/2脉冲长度以及电阻、电感和电容的等效集总元件电路组件。给出了一些方程，基于TLM模拟结果能够实现对射频线圈和样品的全面电磁特性表征。TLM方法的应用扩展到包括安全任意多核脉冲序列的设计，以使组织的比吸收率（SAR）不超过射频线圈组件的安全限值。
