Bio-Effects of Ultra-High MRI Gradient Slew Rates

描述（由申请人提供）：通过应用更强大和快速的磁梯度，可以改善磁共振成像和光谱的空间分辨率和采集时间，从而可能改善心脏成像以及癌症的描绘和检测。不幸的是，梯度场强受到潜在神经和心脏刺激生物效应的限制，并且有效地受到目前无法提供更快转换速率的现有技术的限制。该项目的总体目标是通过改善关键电子子系统的性能来推进MRI技术，该关键电子子系统提供包括所谓的“梯度”（即，磁梯度放大器和相关的梯度线圈）。这些设备用于在磁共振成像实验期间对空间坐标进行编码。“梯度”还用于编码许多其他参数，例如扩散。磁梯度子系统最明显的特征之一是磁场上升时间（也称为“转换速率”）。例如，西门子最近吹嘘其转换速率为400特斯拉/米每秒（400 T/m/s），以100 T/m/s的速度反驳东芝美国公司声称的“市场上最快的转换速率”。当前一代梯度场系统的转换速率受到与潜在神经刺激生物效应相关的安全法规的限制。基于已发表的神经生理学理论研究，我们假设有可能通过大幅减少上升和下降时间持续时间来增加转换速率而不引起不良生物效应。所提出的梯度场转变的改进将利用先前未应用于医疗应用的新型脉冲功率技术来实现。更快的转换速率将提供更快的成像编码时间，这在功能成像和扩散成像以及总体成像速度时间增益（即，更快的多体素磁共振波谱）中可能是有用的。特别是在多参数MRI研究领域，患者的成像时间可能远远超过一小时。更快的转换速率梯度可以减少这个时间和/或允许在同一时间窗口中收集更多信息。该项目的第一阶段将重点建设一个能够产生超快磁场梯度的电气试验台，并使用无脊椎动物模型进行体模测试和原理验证实验。后续阶段将检查脊椎动物和人类志愿者的生物效应。商业化战略将包括与线圈制造商合作定制梯度线圈，并将该技术纳入与商业战略合作伙伴共同构建的新型PET/MRI设备中。公共卫生相关性本项目的总体目标是通过改善提供磁梯度场的关键子系统（即，磁梯度放大器和相关的梯度线圈）。磁梯度子系统最明显的特征之一是磁场上升时间（也称为“转换速率”）。当前一代梯度场系统的转换速率受到与潜在神经刺激生物效应相关的安全法规的限制。基于已发表的神经生理学理论研究，我们假设有可能通过大幅减少上升和下降时间持续时间来增加转换速率而不引起不良生物效应。所提出的梯度场转换的改进将受到以前未应用于医疗应用的新型脉冲功率技术的影响。该项目预计将改善MRI安全性，心脏成像和癌症诊断。

DESCRIPTION (provided by applicant): The spatial resolution and acquisition times for magnetic resonance imaging and spectroscopy could be improved through the application of more powerful and rapid magnetic gradients, thereby potentially leading to improved cardiac imaging and delineation and detection of cancers. Unfortunately, gradient field strength is limited by concerns about potential neural and cardiac stimulation bio-effects and effectively by existing technology that currently does not provide faster slew rates. The overall goal of this project is to advance MRI technology by improving the performance of critical electronic subsystems that deliver magnetic gradient fields comprising what is known as the "gradients" (i.e., magnetic gradient amplifiers, and associated gradient coils). These devices are used for the encoding of spatial coordinates during magnetic resonance imaging experiments. The "gradients" are also used for encoding numerous other parameters such as diffusion. One of the most visible characteristics of magnetic gradient subsystems is the magnetic field rise-time (also known as "slew rate"). For example, Siemens recently boasted of a 400 Tesla per meter per second (400 T/m/s) slew rate, countering a Toshiba America claim of the "fastest slew rate in the market" with 100 T/m/s. The slew rate of the current generation of gradient field systems is limited by safety regulations concerned with potential neural stimulation bio-effects. Based on published theoretical studies on neural physiology, we hypothesize that it is possible to increase slew rates without causing untoward bio-effects, by dramatically reducing rise- and fall-time durations. The proposed improvement in gradient-field transitions will be effected with novel pulsed- power technology that has not been previously applied to medical applications. Faster slew rates would afford faster imaging encoding times that could be useful in functional imaging and diffusion imaging as well as overall imaging speed time gains (i.e. faster multi-voxel magnetic resonance spectroscopy). Especially in the area of multi-parametric MRI studies, imaging times on patients can far exceed one hour. Faster slew rate gradients can reduce this time and or allow for more information gathering in the same time window. Phase I of the project will focus on construction of an electrical test-bed capable of producing ultra-fast magnetic field gradients, with phantom testing and proof-of-principle experiments using an invertebrate animal model. Follow-on phases will examine bio- effects in vertebrate animals and human volunteers. Commercialization strategies will include partnering with a coil manufacturer to customize gradient coils, and the incorporation of the technology in a novel PET/MRI device built in conjunction with a commercial strategic partner. Public Health Relevance The overall goal of this project is to advance MRI technology by improving the performance of critical subsystems that deliver magnetic gradient fields (i.e., magnetic gradient amplifiers, and associated gradient coils). One of the most visible characteristics of magnetic gradient subsystems is the magnetic field rise-time (also known as "slew rate"). The slew rate of the current generation of gradient field systems is limited by safety regulations concerned with potential neural stimulation bio-effects. Based on published theoretical studies on neural physiology, we hypothesize that it is possible to increase slew rates without causing untoward bio-effects, by dramatically reducing rise- and fall-time durations. The proposed improvement in gradient-field transitions will be effected with novel pulsed-power technology that has not been previously applied to medical applications. The project is expected to result in improvements for MRI safety, cardiac imaging, and cancer diagnosis.