Carbunaru R, Durand D M
Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA.
Magn Reson Med. 1997 Nov;38(5):750-8. doi: 10.1002/mrm.1910380511.
The stimulation of axons under MRI magnetic fields is analyzed solving the cable equation along the axons in the presence of magnetic field z gradients. Axons are represented using a one-dimensional compartmental cable model including the kinetics of mammalian myelinated fibers. Computer simulations of the model were performed for sinusoidal and trapezoidal fields. Several axon and field parameters were tested to determine the threshold values for axonal stimulation of the magnetic field, induced electric field and time derivative of the magnetic field. The results indicate that 1) threshold for stimulation is lowest for the largest diameter axons terminating in the region where the magnetic field is maximum, 2) trapezoidal waveforms can be optimized to allow better sub-threshold resolution than sinusoidal waveforms, and 3) the induced electric field is better than the magnetic field and time derivative of the magnetic field as indicators of stimulation threshold.
通过在存在磁场z梯度的情况下沿轴突求解电缆方程，分析了MRI磁场下轴突的刺激情况。使用包含哺乳动物有髓纤维动力学的一维房室电缆模型来表示轴突。对该模型进行了正弦场和梯形场的计算机模拟。测试了几个轴突和场参数，以确定磁场、感应电场和磁场时间导数对轴突刺激的阈值。结果表明：1）终止于磁场最大值区域的最大直径轴突的刺激阈值最低；2）梯形波形可进行优化，以实现比正弦波形更好的亚阈值分辨率；3）作为刺激阈值的指标，感应电场优于磁场和磁场时间导数。
