Oya Hiroyuki, Adolphs Ralph, Howard Matthew A, Michael Tyszka J
Department of Neurosurgery, University of Iowa, Iowa City, IA, USA; Iowa Neuroscience Institute, University of Iowa, Iowa City, IA, USA.
Division of Humanities and Social Sciences, California Institute of Technology, Pasadena, CA, USA.
Neuroimage Clin. 2025;45:103741. doi: 10.1016/j.nicl.2025.103741. Epub 2025 Jan 25.
Electrical-stimulation fMRI (es-fMRI) combines direct stimulation of the brain via implanted electrodes with simultaneous rapid functional magnetic resonance imaging of the evoked response. Widely used to map effective functional connectivity in animal studies, its application to the human brain has been limited due to safety concerns. In particular, the method requires reliable prediction and minimization of local tissue heating close to the electrodes, which will vary with imaging parameters and hardware configurations. Electrode leads for such experiments typically remain connected to stimulators outside the magnet room and cannot therefore be treated as electrically short at the radio frequencies employed for 1.5 T and 3 T fMRI. The potential for significant absorption and scattering of radiofrequency energy from excitation pulses during imaging is therefore a major concern. We report a series of temperature measurements conducted in human brain phantoms at two independent imaging centers to characterize factors effecting RF heating of electrically long leads with body coil transmission at 3 Tesla for temporal RMS RF transmit fields ( [Formula: see text] ) up to 3.5 µT including multiband echo planar imaging and 3D T2w turbo spin echo imaging. Under all conditions tested, with one exception, the temperature rise measured immediately adjacent to electrode contacts in a head-torso phantom with body coil RF transmission was less than 0.75 °C. We provide detailed quantification across a range of configurations and conclude with specific recommendations for cable routing that will help ensure the safety of es-fMRI in humans and provide essential data to institutional review boards.
电刺激功能磁共振成像（es-fMRI）将通过植入电极对大脑的直接刺激与对诱发反应的同步快速功能磁共振成像相结合。它在动物研究中广泛用于绘制有效的功能连接图，但由于安全问题，其在人类大脑中的应用受到限制。特别是，该方法需要可靠地预测并尽量减少靠近电极处的局部组织发热，而这会随成像参数和硬件配置而变化。此类实验的电极导线通常仍连接到磁体室外部的刺激器，因此在1.5T和3T功能磁共振成像所使用的射频频率下，不能将其视为电短导线。因此，成像过程中激发脉冲产生的射频能量显著吸收和散射的可能性是一个主要问题。我们报告了在两个独立成像中心对人脑模型进行的一系列温度测量，以表征在3特斯拉下使用体线圈传输时，对于高达3.5微特斯拉的时间均方根射频发射场（[公式：见原文]），包括多频段回波平面成像和3D T2加权快速自旋回波成像，影响电长导线射频加热的因素。在所有测试条件下，除了一个例外，在使用体线圈射频传输的头 - 躯干模型中，紧邻电极接触点测得的温度上升小于0.75°C。我们提供了一系列配置的详细量化结果，并给出了电缆布线的具体建议，这将有助于确保es-fMRI在人体中的安全性，并为机构审查委员会提供重要数据。
