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

使用磁聚焦电阻抗断层扫描 (mf-EIT) 进行神经监测

• 批准号: 9055423
• 负责人: Daniel Kenneth Freeman
• 金额: $ 29.92万
• 依托单位: CHARLES STARK DRAPER LABORATORY
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-30 至 2017-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9055423
• 关键词: Address; Adopted; Alzheimer' s Disease; Brain; Caliber; Charge; Clinical; Computer Simulation; Devices; Diagnosis; Diffuse; Electrodes; Elements; Epilepsy; Event; Experimental Models; Head; Human; Image; Location; Measurement; Measures; Methods; Modeling; Monitor; Neurologic; Neurosciences; Outcome; Particle Accelerators; Patients; Physiological; Post-Traumatic Stress Disorders; Procedures; Research; Research Personnel; Resolution; Risk; Saline; Scalp structure; Seizures; Signal Transduction; Source; Structure; Techniques; Testing; Time; Work; base; cranium; electric impedance; imaging modality; improved; magnetic field; neuroimaging; non-invasive monitor; particle; public health relevance; relating to nervous system; response; simulation; temporal measurement; tomography; visual stimulus; voltage

 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.

 描述(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来源的程序。这种侵入性的手术有风险，促使人们需要一种非侵入性的技术来检测大脑深处的癫痫发作。一种可能的技术是一种被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发生的局部电阻抗变化。通过使用放置在头皮上的电极向大脑注入小电流，可以检测到阻抗的这种变化。尽管经过了多年的研究，但由于成像质量相对较差，EIT尚未被临床应用于神经成像。例如，研究人员发现，当人类患者接受EIT成像时，可以检测到大脑活动对某些事件(例如视觉刺激)做出反应的变化，但信号极其强烈 规模很小，很难确定活动来自大脑的哪个部位。我们改善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。具体地说，当电流通过头皮电极注入头部时，电流会广泛扩散，结果是，测量结果反映了整个大脑阻抗的任何变化，产生了对神经活动的噪声和不准确的估计。我们的假设是，人们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。我们将采用粒子加速器中广泛使用的一种技术来控制带电粒子的路径：我们将引入一个磁场，基本上将电流引导到受控的路径上通过大脑。我们计划测试以下假设：如果电流通过头皮电极注入大脑，那么施加一个与所施加的电流方向相反的静态磁场将把电流限制在一个小的、平行的体积内。因此，从头皮电极测量到的电压波动将反映大脑中准确位置的神经活动。我们将使用模拟和台式测试来验证这一假设。这些模拟将使我们能够理解外加磁场与通过导电介质的体积电流的路径之间的关系。然后，我们将使用这些发现来指导台式测试，在该测试中，我们使用了由盐水箱制成的头部实验模型和头骨的石膏模型。我们提出的利用磁场引导电流通过大脑的技术有可能显著提高EIT获得的图像质量，从而为神经活动的非侵入性监测提供一种潜在的强大技术。