Authors :
Presenting Author: Tyrell Pruitt, PhD – The University of Texas Southwestern Medical Center
Natascha Fonseca, PhD – Postdoctoral Researcher, Radiology, The University of Texas Southwestern Medical Center; Sasha Alick-Lindstrom, MD – The University of Texas Southwestern Medical Center; Pegah Askari, B.S. – The University of Texas Southwestern Medical Center; Joseph Maldjian, MD – The University of Texas Southwestern Medical Center; Amy Proskovec, PhD – The University of Texas Southwestern Medical Center; Elizabeth Davenport, PhD – The University of Texas Southwestern Medical Center
Rationale:
Cryogenic magnetoencephalography (Cryo-MEG), a traditional technique for identifying and localizing neuronal activity in epileptic patients, is recognized for its high precision but also for its operational complexity and significant costs. A major portion of these costs are attributed to the necessity of liquid helium. Consequently, the access and use of this technology is restricted to larger hospitals and specialized centers, limiting its widespread application. Given this context, the present study aimed to explore an alternative, the Optically Pumped Magnetometer Magnetoencephalography (OPM-MEG) system. The OPM-MEG, characterized by a low sensor count (10) and devoid of the need for liquid helium, was postulated to offer a comparable but not equivalent localization efficiency to Cryo-MEG, thereby emerging as a potential cost-effective alternative in the domain of neuroimaging.Methods: An integrative protocol was developed to comprehensively compare the localization capabilities of both systems. Initially, the patients (n = 3) underwent their routine Cryo-MEG scans following the traditional clinical protocol. Immediately after, a supplementary condensed protocol was administered using the OPM-MEG system. This protocol involved a series of tasks designed to stimulate different regions of the brain: 5- minute resting period, 2-minute epoch baseline, motor task, visual task, and language task. Localization results from both systems were compiled and juxtaposed for a comparative evaluation. Further, epileptic spikes from both acquisition methods were identified by a neurophysiologist. Spikes identified on Cryo-MEG were modeled as per traditional protocol using dipole modeling in the clinical software, while the OPM-MEG spikes were localized using Linearly Constrained Minimum Variance (LCMV) beamforming in the Brainstorm software.
Results:
The OPM-MEG system succeeded in localizing all tasks and epileptic spikes, demonstrating a comparable performance to the Cryo-MEG system. However, it is important to note that the term 'comparable' does not imply equivalent efficiency. While the OPM-MEG offered satisfactory results, it did not surpass or match the superior precision of the Cryo-MEG. The figures visually illustrate the congruent spike localization results from the OPM-MEG and Cryo-MEG scans, offering a clear demonstration of their comparative performance.Conclusions:
The low sensor count OPM-MEG proved to have a reasonable level of source localization capabilities comparable to Cryo-MEG. The ability of OPM-MEG to deliver satisfactory results at a significantly lower operational cost underscores its potential as a valuable alternative to Cryo-MEG, especially in settings with budgetary or space constraints such as epilepsy monitoring units and smaller clinics. By offering comparable localization capabilities, the OPM-MEG could democratize access to critical neuroimaging tools, helping to expand the scope and reach of neuroimaging in epilepsy treatment and research.Funding:
G.R. White Trust, Effie Woffard Cain Endowment, and the Hoblitzelle Foundation