Bio-Effects of Ultra-High MRI Gradient Slew Rates

描述（由申请人提供）：磁共振成像和光谱学的空间分辨率和采集时间可以通过应用更强大和快速的磁梯度来提高，从而有可能改善心脏成像和癌症的描绘和检测。不幸的是，由于考虑到潜在的神经和心脏刺激生物效应，以及现有技术目前无法提供更快的转换速率，梯度场强受到限制。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，这些子系统提供的磁梯度场包括所谓的“梯度”（即磁梯度放大器和相关的梯度线圈）。这些装置在磁共振成像实验中用于空间坐标的编码。“梯度”也用于编码许多其他参数，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“回转率”）。例如，西门子最近吹嘘其每米每秒400特斯拉（400t /m/s）的转换率，以100 T/m/s的转换率对抗东芝美国公司声称的“市场上最快的转换率”。当前一代梯度场系统的旋转速度受到有关潜在神经刺激生物效应的安全规定的限制。根据已发表的神经生理学理论研究，我们假设，通过大幅减少上升和下降的持续时间，可以在不引起不良生物效应的情况下提高转换率。提出的梯度场跃迁的改进将通过新的脉冲功率技术来实现，这种技术以前没有应用于医疗应用。更快的转换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整体成像速度时间增益（即更快的多体素磁共振波谱）中是有用的。特别是在多参数MRI研究领域，对患者的成像时间可以远远超过一个小时。更快的转换率梯度可以减少这个时间，或者允许在同一时间窗口内收集更多的信息。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模拟测试和原理验证实验。后续阶段将在脊椎动物和人类志愿者身上检验生物效应。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。该项目的总体目标是通过改善提供梯度磁场的关键子系统（即，梯度放大器和相关的梯度线圈）的性能来推进MRI技术。磁梯度子系统最明显的特征之一是磁场上升时间（也称为“回转率”）。当前一代梯度场系统的旋转速度受到有关潜在神经刺激生物效应的安全规定的限制。根据已发表的神经生理学理论研究，我们假设，通过大幅减少上升和下降的持续时间，可以在不引起不良生物效应的情况下提高转换率。提出的梯度场转换的改进将通过以前未应用于医疗应用的新型脉冲功率技术来实现。该项目有望改善核磁共振成像的安全性、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.