Portable Magnetometry for Detection of Biomagnetism in Ambient Environments

Limes, Mark; Foley, E. L.; Kornack, T. W.; Caliga, S.; McBride, S. E.; Braun, A.; Lee, W.; Lucivero, Vito Giovanni; Romalis, Michael

doi:10.1103/physrevapplied.14.011002

Cited by 182 publications

(125 citation statements)

References 29 publications

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Section: Results and Discussionmentioning

confidence: 99%

“…The reason is that the curve fitting results are limited by quantization noise of the oscilloscope, while the FPGA readings are of higher precision. An analysis of the FPGA performance can be found in the appendix of [43], while attention has to be paid to the larger baseline and the lower sampling rate used in [43]. Gradiometer spectral density pT/cm/ √ Hz mag1 FPGA mag2 FPGA soft grad FPGA mag1 fits soft grad fits After notch-filtering the photodiode signal, the instantaneous frequency (IF) at a sample rate of 6.25 MHz is computed using the Hilbert transform.…”

Section: Omg Characterization and Performancementioning

confidence: 99%

“…Unshielded MRX has been performed before with SQUID [ 38 ] and fluxgates [ 39 ], while OPM-MRX has been performed in a weakly shielded environment [ 26 ]. Recently, several developments of portable OPM for unshielded operation have been published [ 40 , 41 , 42 , 43 ]. It should be noted, that although not commercially available, the high bandwidth sensor presented in [ 40 ] is also a well suited candidate for unshielded MRX.…”

Section: Introductionmentioning

confidence: 99%

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Pulsed Optically Pumped Magnetometers: Addressing Dead Time and Bandwidth for the Unshielded Magnetorelaxometry of Magnetic Nanoparticles

Jaufenthaler

Kornack

Lebedev

et al. 2021

Sensors

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Magnetic nanoparticles (MNP) offer a large variety of promising applications in medicine thanks to their exciting physical properties, e.g., magnetic hyperthermia and magnetic drug targeting. For these applications, it is crucial to quantify the amount of MNP in their specific binding state. This information can be obtained by means of magnetorelaxometry (MRX), where the relaxation of previously aligned magnetic moments of MNP is measured. Current MRX with optically pumped magnetometers (OPM) is limited by OPM recovery time after the shut-off of the external magnetic field for MNP alignment, therewith preventing the detection of fast relaxing MNP. We present a setup for OPM-MRX measurements using a commercially available pulsed free-precession OPM, where the use of a high power pulsed pump laser in the sensor enables a system recovery time in the microsecond range. Besides, magnetometer raw data processing techniques for Larmor frequency analysis are proposed and compared in this paper. Due to the high bandwidth (≥100 kHz) and high dynamic range of our OPM, a software gradiometer in a compact enclosure allows for unshielded MRX measurements in a laboratory environment. When operated in the MRX mode with non-optimal pumping performance, the OPM shows an unshielded gradiometric noise floor of about 600 fT/cm/Hz for a 2.3 cm baseline. The noise floor is flat up to 1 kHz and increases then linearly with the frequency. We demonstrate that quantitative unshielded MRX measurements of fast relaxing, water suspended MNP is possible with the novel OPM-MRX concept, confirmed by the accurately derived iron amount ratios of MNP samples. The detection limit of the current setup is about 1.37 μg of iron for a liquid BNF-MNP-sample (Bionized NanoFerrite) with a volume of 100 μL.

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Section: Results and Discussionmentioning

confidence: 99%

Section: Omg Characterization and Performancementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Pulsed Optically Pumped Magnetometers: Addressing Dead Time and Bandwidth for the Unshielded Magnetorelaxometry of Magnetic Nanoparticles

Jaufenthaler

Kornack

Lebedev

et al. 2021

Sensors

Self Cite

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“…For these experiments, regardless of the usage of comagnetometer, which is for suppressing the magnetic-field noise, an environment with lower magnetic-field noise is beneficial for further reducing the systematic errors related to magnetic-field variations. Furthermore, a magnetic-field noise level of about tens of fT/Hz

and a wide range of operational magnetic field covering Earth’s magnetic field is attractive for ultralow-field nuclear magnetic resonance [ 52 , 53 ] and for recording bio-magnetic signals from human brain activities [ 54 , 55 ].…”

Section: Discussionmentioning

confidence: 99%

Active Magnetic-Field Stabilization with Atomic Magnetometer

Zhang

Ding

Yang

et al. 2020

Sensors

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A magnetically-quiet environment is important for detecting faint magnetic-field signals or nonmagnetic spin-dependent interactions. Passive magnetic shielding using layers of large magnetic-permeability materials is widely used to reduce the magnetic-field noise. The magnetic-field noise can also be actively monitored with magnetometers and then compensated, acting as a complementary method to the passive shielding. We present here a general model to quantitatively depict and optimize the performance of active magnetic-field stabilization and experimentally verify our model using optically-pumped atomic magnetometers. We experimentally demonstrate a magnetic-field noise rejection ratio of larger than ∼800 at low frequencies and an environment with a magnetic-field noise floor of ∼40 fT/Hz1/2 in unshielded Earth’s field. The proposed model provides a general guidance on analyzing and improving the performance of active magnetic-field stabilization with magnetometers. This work offers the possibility of sensitive detections of magnetic-field signals in a variety of unshielded natural environments.

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“…High precision instruments for magnetic imaging 3 – 5 are contactless and can offer superior outputs than electrical measurements, since magnetic signals are not attenuated by human tissue 6 , 7 . Current technologies for ultra-low magnetic field detection include Superconducting QUantum Interference Devices (SQUID) 8 and Optical Pumping Magnetometry (OPM) 9 , 10 reaching femto-tesla detection levels and more recently Spin Exchange Relaxation Free (SERF) atomic magnetometers on pico-tesla range 11 , 12 . Despite the very low field detection capability, SQUIDs require cryogenic environments 13 and OPMs rely on complex optical parts 14 , hampering a seamless compact and wearable design.…”

Section: Introductionmentioning

confidence: 99%

Two-dimensional arrays of vertically packed spin-valves with picoTesla sensitivity at room temperature

Silva

Franco

Leitao

et al. 2021

Sci Rep

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A new device architecture using giant magnetoresistive sensors demonstrates the capability to detect very low magnetic fields on the pT range. A combination of vertically packed spin-valve sensors with two-dimensional in-plane arrays, connected in series and in parallel, delivers a final detection level of 360 pT/$$\sqrt{Hz}$$ Hz at 10 Hz at room temperature. The device design is supported by an analytical model developed for a vertically packed spin-valve system, which takes into account all magnetic couplings present. Optimization concerning the spacer thickness and sensor physical dimensions depending on the number of pilled up spin-valves is necessary. To push the limits of detection, arrays of a large number of sensing elements (up to 440,000) are patterned with a geometry that improves sensitivity and in a configuration that reduces the resistance, leading to a lower noise level. The final device performance with pT detectivity is demonstrated in an un-shielded environment suitable for detection of bio-signals.

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Portable Magnetometry for Detection of Biomagnetism in Ambient Environments

Cited by 182 publications

References 29 publications

Pulsed Optically Pumped Magnetometers: Addressing Dead Time and Bandwidth for the Unshielded Magnetorelaxometry of Magnetic Nanoparticles

Pulsed Optically Pumped Magnetometers: Addressing Dead Time and Bandwidth for the Unshielded Magnetorelaxometry of Magnetic Nanoparticles

Active Magnetic-Field Stabilization with Atomic Magnetometer

Two-dimensional arrays of vertically packed spin-valves with picoTesla sensitivity at room temperature

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