Simultaneous MEG and ULF MRI for Functional Imaging

描述(由申请人提供)：我们提出了一种新的非侵入性方式，用于同时进行人脑的功能和解剖成像。这将是第一台以高时间分辨率非侵入性测量神经活动的解剖信息和直接后果的仪器。我们建议将脑磁图(MEG)和超低场磁共振成像(ULF-MRI)结合起来。脑磁图(和脑电-EEG)的独特之处在于，它能够以毫秒的时间分辨率非侵入性地测量大脑中的神经活动。超低频磁共振成像是一种激动人心的微区磁场结构成像新技术。MEG和ULF-MRI的信号都是由超导量子干涉装置(SQUID)传感器测量的。因此，MEG和ULF-MRI可以由同一传感器阵列同时采集。虽然相对于高场(HF)，低场下的MR信号会大幅降低，但这里概述的SQUID传感器和超强磁共振成像技术的精致灵敏度将远远弥补这一点。这种新的功能/结构成像模式将通过减少或消除与联合配准相关的许多误差来源(通常为5-10 mm或更大)来增强人脑的神经成像，因为功能和结构将通过单一仪器获得。使用HF和URF表面渲染，HF-MRI可以准确地与脑磁图神经活动共同配准。此外，由于ULF-MRI没有磁化率变化引起的失真，在ULF获得的解剖表面可以使用现有的扭曲算法来校正HF图像的失真。纠正这些失真将通过更准确地描述头部体积和皮质表面的形状(一个重要的来源限制)来改进MEG来源定位。最后，通过一组SQUID传感器获取Ulf-MRI将使用MR传感器阵列技术实现更快的图像采集，这一技术也在HF探索中。同时MEG/ULF-MRI将被证明是一种强大的通用工具，可以用来了解人脑的动态功能/结构关系，基本上是大脑如何工作以及在哪里工作。它将被用于研究认知过程，用于癫痫等病理的非侵入性定位，以及确定手术结果(通过定位与病理相关的功能)，仅举几例。虽然MEG/ULF-MRI将提供一种强大的新神经成像工具，但它将为令人兴奋的未来发展打开大门。高密度阵列脑电可以很好地实现超强磁共振成像、脑磁图和脑电同步的三重模式。最终，有人推测，神经电流的核磁共振特征最终可能导致神经活动的明确定位。虽然神经活动的明确断层扫描定位似乎是可能的，但时间分辨率可能不会好于数十毫秒。超低频磁共振成像可以直接成像神经活动，即使具有适度的时间分辨率，也可以用来限制同时获取的脑磁图信号，提供毫秒或更好的时间分辨率。

DESCRIPTION (provided by applicant): We propose a new noninvasive modality for simultaneous functional and anatomical imaging of the human brain. This will be the first instrument ever to noninvasively measure both anatomical information and direct consequences of neural activity with high temporal resolution. We propose to combine magnetoencephalography (MEG) with ultra-low field magnetic resonance imaging (ULF-MRI). MEG (and electroencephalography - EEG) is unique in the ability to noninvasively measure neural activity in the brain with millisecond temporal resolution. ULF-MRI is an exciting new technique for structural imaging at magnetic fields in the Microtel regime. Signals for MEG and ULF-MRI are both measured by superconducting quantum interference device (SQUID) sensors. Hence MEG and ULF-MRI can be simultaneously acquired by the same sensor array. While MR signals at low field are drastically reduced relative to high-field (HF), the exquisite sensitivity of SQUID sensors and ULF-MRI techniques outlined here will more than compensate. This new functional/structural imaging modality will enhance neuroimaging of the human brain by reducing or eliminating numerous sources of error associated with co-registration (typically 5-10 mm or more), as the function and structure will be acquired with a single instrument. HF-MRI can be accurately co-registered to the MEG neural activity using HF and ULF surface renderings. Moreover, as ULF-MRI is free from distortions caused by susceptibility variations, anatomical surfaces acquired at ULF can be used to correct HF image distortions using existing warping algorithms. Correcting these distortions will improve MEG source localization by more accurately describing the shape of the head volume and the cortical surface (an important source constraint). Finally, acquisition of ULF-MRI by an array of SQUID sensors will enable faster image acquisition using MR sensor array techniques, techniques also being explored at HF. Simultaneous MEG/ULF-MRI will prove to be a powerful and general tool in the quest to understand the dynamic functional/structural relationships in the human brain, basically how and where the brain works. It will be used to study cognitive processes, for noninvasive localization of pathology such as epilepsy, and for determining surgical outcome (by localizing function in relation to pathology), to name a few. While MEG/ULF-MRI will provide a powerful new neuroimaging tool, it will open the door for exciting future developments. A three-fold modality including simultaneous ULF-MRI, MEG and EEG could readily be envisioned with dense array EEG. Ultimately, it has been speculated that NMR signatures of neural currents may eventually lead to unambiguous localization of neural activity. While unambiguous tomographic localization of neural activity appears possible, the temporal resolution will likely be no better than tens of milliseconds. ULF-MRI that may lead to direct imaging of neural activity, even with modest temporal resolution, can be used to constrain the simultaneously acquired MEG signal, providing millisecond or better temporal resolution.