Mitigation of peripheral nerve stimulation (PNS) in MRI

减轻 MRI 中的周围神经刺激 (PNS)

基本信息

批准号：
10596210
负责人：
Bastien Guerin
金额：
$ 59.24万
依托单位：
MASSACHUSETTS GENERAL HOSPITAL
依托单位国家：
美国
项目类别：
财政年份：
2020
资助国家：
美国
起止时间：
2020-05-01 至 2025-01-31
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/10596210
关键词：
Action Potentials Address Amplifiers Atlases Boundary Elements Clinic Clinical Clinical Research Coiled Bodies Dependence Development Diameter Electric Stimulation Electromagnetics Engineering Equipment Esthesia Excision Foundations Freedom Gender Generations Grant Head Head and neck structure Human body Image Industry Standard Magnetic Resonance Imaging Measurement Measures Mechanics Methods Modeling Modernization Morphologic artifacts Motor Nerve Nerve Fibers Nonlinear Dynamics Pain Pattern Performance Peripheral Nerve Stimulation Peripheral Nerves Phase Population Population Heterogeneity Procedures Property Research Resolution Shapes Shoulder Speed Stream System Techniques Technology Testing Tissues Validation Work body system clinical application connectome cost design electric field experimental study healthy volunteer improved in vivo insight magnetic field medical specialties neuroimaging next generation programs prototype research study simulation somatosensory tool volunteer

项目摘要

7. Project Summary/Abstract Peripheral nerve stimulation (PNS) in MRI results from electric fields induced by the switching of gradient coil, which may result in stimulation of the largest nerves in the body (large diameter nerves are easier to excite than small ones). The use of current generation of Gmax=80 mT/m, Smax=200 T/m/s whole-body MRI gradients is largely constrained by PNS rather than amplifier power, mechanical issues or heat removal and specialty coils such as the Gmax=300 mT/m, Smax=200 T/m/s “MGH Connectome” coil can only be fully used within a fraction of its operational parameter space. Impacting these PNS limitations will allow faster imaging, higher resolution and reduced distortions in many sequences routinely used for research and in the clinic for head/neck as well as body imaging, such as EPI, DWI, bSSFP, RARE and PROPELLER. Head-only (HO) gradient inserts have higher thresholds but their latest generation are also PNS limited. Additionally, most neuroimaging research studies and nearly all clinical studies use whole-body (WB) gradient systems. In this program, we develop a gradient design tool with explicit PNS constraints and validate the PNS benefits by experimental tests of optimized WB and HO designs. The state-of- the-art boundary element (BEM)-stream function (SF) approach for designing the winding patterns of gradient coils optimizes the magnetic field subject to electrical, mechanical and thermal constraints, but ignores the primary limiting factor; PNS. Although design rules-of-thumb exist, PNS is not directly incorporated in the design step. Instead, PNS is assessed after construction of a coil prototype on volunteers. This is a costly and slow approach that allows only minimal PNS mitigation iteration. In this proposal, we build on our work modeling magneto-stimulation in full-body peripheral nerve models which takes into account: i) the coil wire pattern, ii) the detailed shaping of the induced electric fields by the tissue boundaries, iii) the dependence of the stimulation effect on the relative orientation between electric field and nerves, iv) the non-linear nerve dynamics and their differing properties depending on class (motor, somatosensory or autonomic) and branching distance from the CNS. Our preliminary results indicate that we can increase PNS thresholds by 2X for WB and 1.7X for HO designs. The cost is a moderate increase of the linearity error (5%) and inductance (32%, only required for WB designs). This shows that winding patterns intrinsically contain degrees-of-freedom that can support substantial PNS improvements if one has the tools to uncover them during the design phase. We therefore incorporate our PNS analysis into an industry-standard BEM-SF design optimization framework and validate our results by building and testing the best coil designs in a PNS threshold study of healthy volunteers.

7. 项目总结/摘要 MRI 中的周围神经刺激 (PNS) 是由开关引起的电场产生的梯度线圈，这可能会刺激体内最大的神经（大直径神经）比小的更容易激发）。目前使用的Gmax=80 mT/m，Smax=200。 T/m/s 全身 MRI 梯度很大程度上受 PNS 而不是放大器功率的限制，机械问题或散热和特种线圈，例如 Gmax=300 mT/m、Smax=200 T/m/s “MGH Connectome”线圈只能在其操作参数空间的一小部分内充分使用。影响这些 PNS 限制将允许更快的成像、更高的分辨率并减少失真。许多序列通常用于研究和临床中的头/颈部以及身体成像，例如 EPI、DWI、bSSFP、RARE 和 PROPELLER 梯度插入物具有更高的梯度。阈值，但他们的最新一代也受到 PNS 的限制，此外，大多数神经影像学研究。研究和几乎所有临床研究都使用全身 (WB) 梯度系统。在这个程序中，我们开发了一个具有显式 PNS 约束的梯度设计工具，通过优化 WB 和 HO 设计的实验测试来验证 PNS 的优势。用于设计绕组模式的最先进的边界元（BEM）-流函数（SF）方法梯度线圈优化受电气、机械和热约束的磁场，但忽略了主要的限制因素；虽然存在设计经验法则，但 PNS 并不是直接的。相反，PNS 在构建线圈原型后进行评估。这是一种成本高昂且缓慢的方法，仅允许最小限度的 PNS 缓解迭代。这项提案，我们以全身周围神经磁刺激建模工作为基础模型考虑了：i) 线圈线型，ii) 感应线圈的详细形状组织边界的电场，iii) 刺激效果对相对强度的依赖性电场和神经之间的方向，iv) 非线性神经动力学及其不同属性取决于类别（运动、体感或自主）和分支距离 CNS。我们的初步结果表明，我们可以将 WB 的 PNS 阈值提高 2 倍，将 1.7 倍提高。对于 HO 设计，代价是线性误差 (5%) 和电感 (32%，仅) 的适度增加。 WB 设计所需的）这表明缠绕模式本质上包含自由度。如果人们有工具在这一过程中发现它们，那么可以支持 PNS 的重大改进因此，我们将 PNS 分析纳入行业标准 BEM-SF 设计中。优化框架并通过在 PNS 中构建和测试最佳线圈设计来验证我们的结果健康志愿者的阈值研究。