MRI Gradient Coils with Improved Stimulation Threshold

描述(由申请人提供)： 有了目前可用的高功率梯度放大器，磁共振成像(MRI)研究需要强大的、快速切换的梯度场，由于PNS的感应，在速度、分辨率或精度方面都受到限制。他们建议开发、应用和验证一种考虑周围神经刺激(PNS)的准确、高效的梯度线圈设计方法： 具体目标1：建立快速、准确的三维数值计算方法，用于计算脉冲磁线圈作用下弱导电介质样品中的电场分布。这将通过以下方式完成：1.作为金标准的磁线圈在简单液体体模中感应电场的测量，2.通过与金标准实验测量相比较，对现有和建议的数值方法进行评估。 具体目标2：建立PNS阈值的计算场校准。这将通过以下步骤来完成：1.测量暴露于现有高强度头部梯度线圈的人类受试者中的刺激阈值和位置，以及2.计算头部梯度线圈中的真实多组织人体模型中的电场，并识别与测量的PNS阈值相对应的刺激位置中的电场值。 具体目的3：使用经过校准的数值计算来设计具有改进的PNS阈值的磁头梯度线圈原型，并验证其在人体中的性能。这将通过以下步骤完成：1.计算几种候选梯度线圈设计的PNS阈值的变化，并使用优化程序来确定最佳设计；2.构建最优线圈的原型；3.验证原型线圈中人类志愿者改进的PNS阈值。 实现这些目标将需要对磁场和人体之间的相互作用进行重大的工程设计。随着计划的宣布，这项提议将产生仪器(梯度线圈)、技术(线圈设计方法)和软件(场计算和线圈设计算法)，朝着更强大、更精确的生物医学研究技术发展。这项工作将为开发临床上有用的头部和身体梯度线圈奠定基础，这些线圈在诱导PNS之前可以超过现有的线圈。

DESCRIPTION (provided by applicant): With currently available high-power gradient amplifiers, magnetic resonance imaging (MRI) studies requiring strong, rapidly switched gradient fields are limited in speed, resolution, or accuracy due to the induction of PNS. They propose to develop, apply, and verify an accurate and efficient method for gradient coil design with consideration of peripheral nerve stimulation (PNS): SPECIFIC AIM 1: Develop fast and accurate 3 dimensional (3D) numerical method to calculate the electric fields induced in weakly conductive dielectric samples during the operation of pulsed magnetic coils. This will be accomplished by: 1. measurement of the electrical fields induced in simple liquid phantoms by magnetic coils to serve as a gold standard, 2. evaluation of existing and proposed numerical methods by comparison to gold standard experimental measurements. SPECIFIC AIM 2: Establish a calibration of calculated fields to PNS thresholds. This will be accomplished by: 1. measurement of stimulation thresholds and locations in human subjects exposed to existing high strength head gradient coils and, 2. calculation of electrical fields in a realistic multi-tissue human model in the head gradient coil and identification of electrical field values in locations of stimulation corresponding to the measured PNS thresholds. SPECIFIC AIM 3: Use calibrated numerical calculations to design a prototype head gradient coil with improved PNS threshold and verify performance in human subjects. This will be accomplished by: 1. calculation of PNS thresholds for variations of several candidate gradient coil designs and using optimization routine to identify optimal design, 2. construction of a prototype of the optimal coil, 3. verification of improved PNS thresholds of human volunteers in the prototype coil. Accomplishment of these aims will require significant engineering of the interaction between magnetic fields and the human body. In line with the program announcement, this proposal will produce instruments (gradient coils), techniques (coil design methods), and software (field calculation and coil design algorithms) toward more powerful and more precise technology for biomedical research. This work will lay the foundation for development of clinically useful head and body gradient coils that can outperform existing coils before inducing PNS.