A Cryogen-Free, Low-Cost Atomic Magnetometer Array for Magnetoencephalography

描述(申请人提供)：功能神经成像在了解神经回路方面取得了重要进展，并已成为研究精神和神经疾病(如精神分裂症、痴呆症、抑郁症和癫痫)的重要技术，在这些疾病中，解剖成像为阴性或仅显示非特异性发现。脑磁图(MEG)是唯一一种能够以亚厘米级空间分辨率和毫秒级时间分辨率直接测量神经活动的无创功能神经成像技术，但由于其高昂的获取和操作成本，其作为研究和临床工具的潜力尚未在大型SCAE上实现。很大一部分成本来自超导量子干涉装置(SQUID)磁传感器的使用，这种传感器必须用液氦冷却。低温基础设施导致了一个庞大的MEG系统，该系统需要安装一个大的磁屏蔽室来实现可接受的低本底水平，并且具有不能根据磁头大小调整的固定传感器阵列几何形状。这项拟议工作的目标是开发一种小型、低成本的MEG系统，使用原子磁强计(AM)阵列来替代SQUID。AM可以达到与SQUID相当的灵敏度，但不需要低温冷却。AM通过激光询问测量磁场与玻璃池内原子之间的相互作用，从而检测磁场。最近，我们开发了一种紧凑型光纤耦合AM，并将其用于检测人体脑磁图信号。在这些初步研究的基础上，我们建议开发一种具有部分头部覆盖(大约12厘米×12厘米)的36通道AM阵列，能够检测和定位神经元活动。在具体目标#1中，我们将设计拟议的AM MEG系统的关键组件，包括用作阵列元素的单个AM和一个人大小的磁屏蔽，以容纳AM阵列和人体对象。商业上可用的磁源定位软件将适应我们的阵列几何结构。将构建一个AM，其性能将在&gt；100赫兹带宽和20 FT/Hz1/2灵敏度的GO/NO-GO规格下进行验证。在具体目标#2中，将构建AM脑磁图系统，并通过检测具有重新配置的AM阵列几何形状以模拟各种头部尺寸的脑磁图模型来确定其源定位精度。人体研究只有在证明了亚厘米的空间分辨率之后才会开始。在具体目标#3中，AM系统将与商业鱿鱼脑磁图系统进行比较，方法是测量两个系统对受试者正中神经和听觉刺激的诱发反应。成功的比较将从强度和位置方面识别神经源，使其在两个系统之间的标准偏差范围内。预计拟议工作的结果将为开发一种全头部覆盖、低成本的AM MEG系统扫清道路，该系统可以适应各种头部尺寸。 与公共健康相关：脑磁图(MEG)是一种有价值的功能神经成像工具，因为它可以以亚厘米的空间分辨率(比EEG更好)和毫秒的时间分辨率(比功能MRI更好)直接测量神经活动，但由于其高昂的采购成本(250万美元)和年度运营成本(&gt；20万美元)，其潜力尚未大规模实现。该项目的目标是开发一个MEG系统，用不需要液氦冷却的原子磁强计阵列取代目前笨重的液氦冷却传感器，以及目前需要一个人大小的磁屏蔽的大型磁屏蔽室。基于原子磁强计的MEG系统将提供大量的成本节约，增加MEG的可用性，缩小设备的尺寸，用于潜在的便携式应用，并能够调整MEG头盔的大小，增加设备的实用性，特别是对儿童。

DESCRIPTION (provided by applicant): Functional neuroimaging has led to important advances in understanding neural circuits and has emerged as an important technique in the study of psychiatric and neurological disorders such as schizophrenia, dementia, depression, and epilepsy, where anatomical imaging is negative or shows only nonspecific findings. Magnetoencephalography (MEG) is the only noninvasive functional neuroimaging technique able to directly measure neural activity with sub-centimeter spatial and millisecond temporal resolution, but its potential as a research and clinical tool has yet to be realized on a large scae due to its high acquisition and operating costs. A large portion of the cost results from the use o superconducting quantum interference device (SQUID) magnetic sensors that must be cooled with liquid helium. The cryogenic infrastructure results in a bulky MEG system that requires installation of a large magnetically shielded room to achieve acceptably low background levels and that has a fixed sensor array geometry that cannot be adjusted for head size. The goal of the proposed work is to develop a small, low-cost MEG system using an array of atomic magnetometers (AMs) as replacements for SQUIDs. AMs can achieve sensitivities comparable to SQUIDs but do not require cryogenic cooling. AMs detect magnetic fields by measuring, via laser interrogation, the interaction between a magnetic field and atoms contained within a glass cell. Recently, we developed a compact optical fiber-coupled AM and used it to detect MEG signals from human subjects. Based on these preliminary studies, we propose to develop a 36-channel array of AMs with partial-head coverage (roughly 12 cm X 12 cm) that is able detect and localize neuronal activity. In Specific Aim #1, we will design critical components of the proposed AM MEG system, including the individual AMs that serve as array elements and a person-sized magnetic shield to contain the AM-array and the human subject. Commercially available magnetic source localization software will be adapted to our array geometry. One AM will be constructed and its performance will be verified at go/no-go specifications of >100 Hz bandwidth and 20 fT/Hz1/2sensitivity. In Specific Aim #2, the AM MEG system will be constructed and its source localization accuracy will be determined by detecting an MEG phantom with the AM array geometry reconfigured to mimic a variety of head sizes. Human studies will commence only after demonstrating sub-centimeter spatial resolution. In Specific Aim #3, the AM system will be compared to a commercial SQUID MEG system by measuring the evoked response in human subjects from median nerve and auditory stimuli with both systems. A successful comparison will identify a neural source in terms of strength and location to within one standard deviation error between the two systems. The results of the proposed work are expected to clear the path for developing a full-head- coverage low-cost AM MEG system that can be adapted to accommodate a wide variety of head sizes. PUBLIC HEALTH RELEVANCE: Magnetoencephalography (MEG) is a valuable tool for functional neuroimaging because it can directly measure neural activity with sub-centimeter spatial resolution (better than EEG) and millisecond temporal resolution (better than functional MRI), but its potential has yet to be realized on a large scale due to its high acquisition costs ( $2.5 million) and annual operating costs (> $200,000). This goal of this project is to develop an MEG system that replaces the current bulky liquid helium cooled sensors with an array of atomic magnetometers that do not require liquid helium cooling and the large magnetically shielded room currently required with a person-sized magnetic shield. An atomic magnetometer-based MEG system would provide substantial cost savings increasing the availability of MEG, a reduction size of the device for potential portable applications, and the ability adjust the size o the MEG helmet increasing the utility of the device particularly with children.