MRI Gradient Coils with Improved Stimulation Threshold

描述（由申请人提供）： 使用目前可用的高功率梯度放大器，需要强、快速切换梯度场的磁共振成像（MRI）研究由于PNS的诱导而在速度、分辨率或准确性方面受到限制。 他们建议开发、应用和验证一种准确有效的梯度线圈设计方法，并考虑外周神经刺激（PNS）： 具体目标1：开发快速准确的三维（3D）数值方法，用于计算脉冲电磁线圈操作期间弱导电介质样品中感应的电场。 这将通过以下方式实现：1.测量由磁线圈在简单液体幻影中诱导的电场以用作金标准，2.通过与金标准实验测量的比较，评估现有和拟议的数值方法。 具体目标2：建立计算场与PNS阈值的校准。 这将通过以下方式实现：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，以及识别对应于所测量的PNS阈值的刺激位置中的电场值。 具体目标3：使用校准的数值计算设计具有改进的PNS阈值的原型头部梯度线圈，并验证在人类受试者中的性能。 这将通过以下方式实现：1.计算针对若干候选梯度线圈设计的变化的PNS阈值，并且使用优化例程来识别最优设计，2.构造最佳线圈的原型，3.在原型线圈中验证人类志愿者的改善的PNS阈值。 要实现这些目标，就需要对磁场与人体之间的相互作用进行重大的工程设计。 根据计划公告，该提案将生产仪器（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），以实现更强大，更精确的生物医学研究技术。 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之前可以优于现有线圈。

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.