Neural Monitoring with Magnetically-Focused Electrical Impedance Tomography (mf-EIT)

 描述（由申请人提供）：临床神经科学非常需要改进的非侵入性监测大脑活动的方法。例如，癫痫患者经常接受将电极插入大脑以定位癫痫发作源的手术。这种侵入性的手术具有风险，因此需要一种非侵入性的技术来检测大脑深处的癫痫发作。一种可能的技术是称为电阻抗断层扫描（EIT）的成像方式，它检测神经活动期间大脑内电阻抗的局部变化。这种阻抗的变化是通过使用放置在头皮上的电极向大脑注入小电流来检测的。尽管经过多年的研究，EIT尚未被用于神经成像的临床应用，因为图像的质量相对较差。例如，研究人员已经发现，当人类患者经历EIT成像时，有可能检测到响应于某些事件（例如视觉刺激）的大脑活动的变化，但是信号非常复杂。 它很小，很难定位大脑中的活动来自哪里。我们提高EIT图像质量的方法是解决我们认为这项技术的核心限制：无法控制注入电流通过大脑的路径。具体来说，当电流通过头皮电极注入头部时，电流会广泛扩散，因此，测量结果反映了整个大脑阻抗的任何变化，从而产生了对神经活动的嘈杂和不精确的估计。我们的假设是，可以通过提高控制电流通过大脑的路径的能力来提高EIT图像的质量。我们将采用一种在粒子加速器中广泛使用的技术来控制带电粒子的路径：我们将引入一个磁场，该磁场将基本上引导电流以受控的路径通过大脑。我们计划测试以下假设：如果电流通过头皮电极注入大脑，则在所施加的电流方向上施加静磁场将起到将电流限制在小的准直体积内的作用。因此，从头皮电极测量的电压波动将反映大脑内精确位置的神经活动。我们将测试这一假设usin模拟和台式测试。模拟将使我们能够理解所施加的磁场和体积电流通过导电介质的路径之间的关系。然后，我们将使用这些发现来指导实验室测试，其中我们使用由盐水罐制成的头部实验模型和头骨石膏模型。我们提出的技术，通过大脑的磁场引导电流有可能显着提高EIT获得的图像质量，产生一个潜在的强大的技术，非侵入性监测神经活动。

 DESCRIPTION (provided by applicant): There is a great need in clinical neuroscience for improved methods of non-invasively monitoring brain activity. For example, patients with epilepsy often undergo procedures in which electrodes are inserted into their brain to localize the source of seizures. Such invasive procedures carry risk, motivating the need for a non-invasive technique that could detect seizures deep in the brain. One possible technique is an imaging modality known as electrical impedance tomography (EIT), which detects local changes in electrical impedance within the brain that occur during neural activity. Such changes in impedance are detected by injecting small currents through the brain using electrodes that are placed on the scalp. Despite many years of research, EIT has not been adopted for clinical use in neuroimaging because the quality of the images is relatively poor. For example, researchers have found that when a human patient undergoes EIT imaging, it is possible to detect a change in brain activity in response to some event (e.g. a visual stimulus), but the signals are extremely small and it is difficult to localize where in the brain the activity is coming from. Our approach o improving the quality of EIT images is to address what we believe is the core limitation of this technique: the inability to control the path of the injected current through the brain. Specificall, when current is injected into the head via scalp electrodes, the current diffuses widely, and as a result, the measurements reflect any changes in impedance throughout the brain, producing a noisy and imprecise estimate of neural activity. Our hypothesis is that one can improve the quality of EIT images by improving the ability to control the path of the current through the brain We will adopt a technique that is widely used in particle accelerators to control the path of charged particles: we will introduce a magnetic field that will essentially steer the current through the brain in a controlled path. We plan to test the following hypothesis: if current is injected into the brain through scalp electrodes, then the application of a static magnetic field i the direction of the applied current flow will act to confine the current to a small, collimated volume. As a result, fluctuations in voltage that are measured from the scalp electrodes will reflect neural activity from a precise location within the brain. We will test this hypothesis usin both simulations and benchtop testing. The simulations will allow us to understand the relationship between an applied magnetic field and the path of the volumetric current flow through a conductive medium. We will then use these findings to guide the benchtop testing, in which we use experimental models of the head made from a saline tank and a plaster model of the skull. Our proposed technique of steering currents through the brain with magnetic fields has the potential to significantly improve the quality of images obtained by EIT, yielding a potentiall powerful technique for non-invasive monitoring of neural activity.