Four-channel optically pumped atomic magnetometer for magnetoencephalography

Colombo, Anthony P.; Carter, Tony R.; Borna, Amir; Jau, Yuan‐Yu; Johnson, Cort; Dagel, Amber L.; Schwindt, Peter D. D.

doi:10.1364/oe.24.015403

Cited by 129 publications

(74 citation statements)

References 40 publications

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“…Better shot-noise limited magnetic field resolutions (in the 1 fT/√Hz range for active cell volumes of about 100 mm 3 ) are presently only achieved with magnetometers working in the SERF mode [28,51,52,53]. However, these magnetometers can only work in near-zero ambient magnetic fields, whereas the LSD-Mz magnetometer operates at Earth’s field strength (about B 0 = 50 μT).…”

Section: Discussionmentioning

confidence: 99%

An Optically Pumped Magnetometer Working in the Light-Shift Dispersed Mz Mode

Schultze

Schillig

IJsselsteijn³

et al. 2017

Sensors

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We present an optically pumped magnetometer working in a new operational mode—the light-shift dispersed Mz (LSD-Mz) mode. It is realized combining various features; (1) high power off-resonant optical pumping; (2) Mz configuration, where pumping light and magnetic field of interest are oriented parallel to each other; (3) use of small alkali metal vapor cells of identical properties in integrated array structures, where two such cells are pumped by circularly polarized light of opposite helicity; and (4) subtraction of the Mz signals of these two cells. The LSD-Mz magnetometer’s performance depends on the inherent and very complex interplay of input parameters. In order to find the configuration of optimal magnetometer resolution, a sensitivity analysis of the input parameters by means of Latin Hypercube Sampling was carried out. The resulting datasets of the multi-dimensional parameter space exploration were assessed by a subsequent physically reasonable interpretation. Finally, the best shot-noise limited magnetic field resolution was determined within that parameter space. As the result, using two 50 mm3 integrated vapor cells a magnetic field resolution below 10 fT/√Hz at Earth’s magnetic field strength is possible.

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Section: Discussionmentioning

confidence: 99%

An Optically Pumped Magnetometer Working in the Light-Shift Dispersed Mz Mode

Schultze

Schillig

IJsselsteijn³

et al. 2017

Sensors

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“…The probe-beam is coaligned with the pump-beam, and as it passes through the rubidium vapor, its polarization rotates through Faraday rotation [20]. The change in orientation of the probe beam's polarization is proportional to the sensed magnetic flux density [8]. The magnetic sensor of our system is the OPM, described in [8] (Fig.…”

Section: A Magnetic Sensormentioning

confidence: 99%

“…The OPM sensor's schematic[8]. PBS: polarizing beam splitter; PM: polarization maintaining, PD: photodiode, λ/2: half wave plate, λ/4: quarter wave plate.…”

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confidence: 99%

Non-Invasive Functional-Brain-Imaging with an OPM-based Magnetoencephalography System

et al. 2020

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A non-invasive functional-brain-imaging system based on optically-pumped-magnetometers (OPM) is presented. The OPM-based magnetoencephalography (MEG) system features 20 OPM channels conforming to the subject's scalp. Due to proximity (12 mm) of the OPM channels to the brain, it is anticipated that this MEG system offers an enhanced spatial resolution as it can capture finer spatial features compared to traditional MEG systems employing superconducting quantum interference device (SQUID). We have conducted two MEG experiments on three subjects: somatosensory evoked magnetic field (SEF) and auditory evoked magnetic field (AEF) using our OPM-based MEG system and a commercial SQUID-based MEG system. We have cross validated the robustness of our system by calculating the distance between the location of the equivalent current dipole (ECD) yielded by our OPM-based MEG system and the ECD location calculated by the commercial SQUID-based MEG system. We achieved sub-centimeter accuracy for both SEF and AEF responses in all three subjects.

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“…Additionally, SERF OPMs can be miniaturised (Shah et al 2007;Knappe et al 2011), enabling the construction of high-density sensor arrays. SERF OPMs with sensitivities better than 5 fT/ Hz have been demonstrated (Kominis et al 2003;Griffith et al 2010;Colombo et al 2016;Knappe et al 2016).…”

Section: Introductionmentioning

confidence: 98%

Requirements for coregistration accuracy in on-scalp MEG

Zetter

Iivanainen

Stenroos

et al. 2017

Preprint

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Optically-pumped magnetometers (OPMs) have recently reached sensitivity levels that enable their use in magnetoencephalography (MEG). In contrast to the SQUID sensors used in current MEG systems, OPMs do not require cryogenic cooling and can thus be placed within millimetres from the head, enabling the construction of on-scalp sensor arrays that conform to the shape of the head. To properly estimate the location of neural sources within the brain, one must accurately know the position and orientation of sensors in relation to the head. With the adaptable on-scalp MEG sensor arrays, this coregistration becomes more challenging than in current SQUID-based MEG systems that use rigid sensor arrays.Here, we used simulations to quantify how accurately one needs to know the position and orientation of sensors in an on-scalp MEG system, and how different types of localisation errors affect forward modelling and source estimates obtained by minimum-norm estimation and dipole fitting.We found that sensor position errors generally have a larger effect than orientation errors and that these errors affect the localisation accuracy of superficial sources the most. Based on our results, we propose < 4-mm RMS sensor position and < 10• RMS sensor orientation error levels as a requirement for source estimation with the above-mentioned methods in on-scalp MEG to obtain similar or higher accuracy than with current SQUID-based MEG systems.

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Four-channel optically pumped atomic magnetometer for magnetoencephalography

Cited by 129 publications

References 40 publications

An Optically Pumped Magnetometer Working in the Light-Shift Dispersed Mz Mode

An Optically Pumped Magnetometer Working in the Light-Shift Dispersed Mz Mode

Non-Invasive Functional-Brain-Imaging with an OPM-based Magnetoencephalography System

Requirements for coregistration accuracy in on-scalp MEG

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