Xu Bin, Wei Qing, Liu Feng, Crozier Stuart
School of Information Technology and Electrical Engineering, University of Queensland, Brisbane QLD 4072, Australia.
IEEE Trans Biomed Eng. 2005 Sep;52(9):1582-7. doi: 10.1109/TBME.2005.851514.
An inverse methodology for the design of biologically loaded radio-frequency (RF) coils for magnetic resonance imaging applications is described. Free space time-harmonic electromagnetic Green's functions and de-emphasized B1 target fields are used to calculate the current density on the coil cylinder. In theory, with the B1 field de-emphasized in the middle of the RF transverse plane, the calculated current distribution can generate an internal magnetic field that can reduce the central overemphasis effect caused by field/tissue interactions at high frequencies. The current distribution of a head coil operating at 4 T (170 MHz) is calculated using an inverse methodology with de-emphasized B1 target fields. An in-house finite-difference time-domain routine is employed to evaluate B1 field and signal intensity inside a homogenous cylindrical phantom and then a complete human head model. A comparison with a conventional RF birdcage coil is carried out and demonstrates that this method can help in decreasing the normal bright region caused by field/tissue interactions in head images at 170 MHz and higher field strengths.
描述了一种用于磁共振成像应用的生物负载射频（RF）线圈设计的逆向方法。利用自由空间时谐电磁格林函数和去加重的B1目标场来计算线圈圆柱体上的电流密度。理论上，通过在RF横向平面中间去加重B1场，计算出的电流分布可以产生一个内部磁场，该磁场可以减少高频下场/组织相互作用引起的中心过度强调效应。使用具有去加重B1目标场的逆向方法计算了工作在4 T（170 MHz）的头部线圈的电流分布。采用内部时域有限差分程序来评估均匀圆柱形模型以及完整人头模型内部的B1场和信号强度。与传统的RF鸟笼线圈进行了比较，结果表明该方法有助于减少170 MHz及更高场强下头部图像中场/组织相互作用导致的正常亮区。
