Abstract
Scalar optically-pumped magnetometers (OPMs) are being developed in small packages with high sensitivities. The high common-mode rejection ratio of these sensors allows for detection of very small signals in the presence of large background fields making them ideally suited for brain imaging applications in unshielded environments. Despite a flurry of activity around the topic, questions remain concerning how well a dipolar source can be localized under such conditions, especially when using few sensors. In this paper, we investigate the source localization capabilities using an array of scalar OPMs in the presence of a large background field while varying dipole strength, sensor count, and forward model accuracy. We also consider localization performance as the orientation angle of the background field changes. Our results are validated experimentally through accurate localization using a phantom virtual array mimicking a current dipole in a conducting sphere in a large background field. Our results are intended to give researchers a general sense of the capabilities and limitations of scalar OPMs for magnetoencephalography systems.
Highlights
Magnetoencephalography (MEG) is a non-invasive method to image brain function with high spatial and temporal resolution [1]
We provide numerical characterizations of localization accuracy based on the variability in sensor count, sensitivity, and the fidelity of the forward model using a single dipolar source in a conducting sphere and large ambient field
We considered single-source dipole localization with scalar optically-pumped magnetometers (OPMs) arrays in large uniform ambient fields
Summary
Magnetoencephalography (MEG) is a non-invasive method to image brain function with high spatial and temporal resolution [1]. The narrow linewidths of SERF OPMs [7, 8] limit the operating dynamic range to a few nano-Tesla or near zero-field background This means magnetically shielded rooms (MSRs), and often additional large coils, are necessary to cancel any ambient fields and reduce interference that can severely limit usefulness in hospital environments. An alternative to zero-field OPMs are total-field or scalar optically-pumped magnetometers, which are being developed in microfabricated packages [9] or with high sensitivities [10] While they were first developed in the 1950s [11] and used for biomagnetic measurements since the 1970s [12], only recently have they reached noise floors sufficient for MEG applications and been demonstrated in small packaged sensors [13]. Total field magnetometers realize higher common-mode rejection ratios than their vector counterparts [14] This allows for the detection of very small signals in the presence of large background fields, making them well suited for use in unshielded environments [15, 16]. We illustrate the validity of our method by localizing a current dipole using a dry phantom and a scalar gradiometer array
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
