Publications
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Investigation of Converse Magnetoelectric Thin-Film Sensors for Magnetocardiography
Authors: Eric Elzenheimer, Patrick Hayes, Lars Thormählen, Erik Engelhardt, Adrian Zaman, Eckhard Quandt, Norbert Frey, Michael Höft, Gerhard Schmidt
Publication Date: 2023-13-15
Venue: IEEE Sensors
DOI: 10.1109/JSEN.2023.3237910
Keywords: Sensors, Magnetoelelectric effects, Magnetic sensors, Magnetostriction, Magnetic shielding, Magnetic resonance, Magnetic noise
Abstract: In this paper, we highlight the development of thin-film magnetoelectric (ME) sensors as promising candidates for biomagnetic sensing, specifically in magnetocardiography (MCG). In our pilot study with a healthy volunteer in a magnetically shielded chamber, we applied an ME prototype (converse ME thin-film sensors) for the first time. Our sensor achieved a noise amplitude spectral density below 20 pT/√Hz at 10 Hz using a sophisticated magnetic layer system. We successfully detected the magnetic equivalent of a human R wave within a one-minute measurement period, demonstrating the potential of ME sensors for non-invasive cardiovascular applications.
BibTeX Citation
@article{elzenheimer2023investigation, title={Investigation of converse magnetoelectric thin-film sensors for magnetocardiography}, author={Elzenheimer, Eric and Hayes, Patrick and Thorm{\"a}hlen, Lars and Engelhardt, Erik and Zaman, Adrian and Quandt, Eckhard and Frey, Norbert and H{\"o}ft, Michael and Schmidt, Gerhard}, journal={IEEE Sensors Journal}, volume={23}, number={6}, pages={5660--5669}, year={2023}, publisher={IEEE} doi={10.1109/JSEN.2023.3237910} }
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Non-Invasive Electroanatomical Mapping: A State-Space Approach for Myocardial Current Density Estimation
Authors: Erik Engelhardt, Eric Elzenheimer, Johannes Hoffmann, Christy Meledeth, Norbert Frey, Gerhard Schmidt
Publication Date: 2023-12-16
Venue: Bioengineering
DOI: 10.3390/bioengineering10121432
Keywords: Biomagnetism, Magnetocardiography, Non-invasive cardiac diagnostics, Kalman filter, Gradient descent optimization
Abstract: We introduce a new system state-based method for non-invasively estimating the electrical activity of the human heart using magnetocardiographic (MCG) measurements. Our algorithm employs a Kalman filter and gradient descent optimization to learn cardiac propagation paths, potentially reducing patient risks associated with invasive procedures and improving treatment planning.
BibTeX Citation
@article{engelhardt_noninvasive_2023, title={Non-Invasive Electroanatomical Mapping: A State-Space Approach for Myocardial Current Density Estimation}, author={Engelhardt, Erik and Elzenheimer, Eric and Hoffmann, Johannes and Meledeth, Christy and Frey, Norbert and Schmidt, Gerhard}, journal={Bioengineering}, volume={10}, number={12}, pages={1432}, year={2023}, publisher={MDPI}, doi = {10.3390/bioengineering10121432} }
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Kiel Cardio Database
Authors: Erik Engelhardt, Norbert Frey, Gerhard Schmidt
Publication Date: 2023-12-15
Venue: PhysioNet
DOI: 10.13026/q6r2-zz68
Keywords: Database, Magnetocardiography, Optically Pumped Magnetometer
Abstract: In this paper, we present the Kiel Cardio Database, containing magnetocardiography (MCG) measurements from seven healthy male volunteers recorded using QuSpin QZFM Gen 1 sensors in a magnetically shielded chamber. By making this dataset publicly available, we aim to enable researchers without access to specialized equipment to advance MCG research.
BibTeX Citation
@misc{engelhardt_kiel_2023, title = {Kiel Cardio Database}, url = {https://physionet.org/content/kiel-cardio/1.0.0/}, doi = {10.13026/Q6R2-ZZ68}, publisher = {PhysioNet}, author = {Engelhardt, Erik and Frey, Norbert and Schmidt, Gerhard}, }
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A Concept for Myocardial Current Density Estimation with Magnetoelectric Sensors
Authors: Erik Engelhardt, Eric Elzenheimer, Johannes Hoffmann, Tobias Schmidt, Adrian Zaman, Norbert Frey, Gerhard Schmidt
Publication Date: 2023-09-20
Venue: Current Directions in Biomedical Engineering
DOI: 10.1515/cdbme-2023-1023
Keywords: Biomagnetism, Magnetocardiography, Magnetoelectric sensors, Noninvasive cardiac diagnostics
Abstract: We present a novel noninvasive approach to estimate cardiac current densities using magnetocardiography (MCG). Our algorithm utilizes nested optimization and first-order Thiran all-pass filters to model current propagation between equally-sized myocardial voxels, showing potential to complement or replace invasive catheter-based procedures for localizing arrhythmogenic tissue.
BibTeX Citation
@inproceedings{engelhardt_concept_2023, title={A Concept for Myocardial Current Density Estimation with Magnetoelectric Sensors}, author={Engelhardt, Erik and Elzenheimer, Eric and Hoffman, Johannes and Schmidt, Tobias and Zaman, Adrian and Frey, Norbert and Schmidt, Gerhard}, booktitle={Current Directions in Biomedical Engineering}, volume={9}, number={1}, pages={89--92}, year={2023}, organization={De Gruyter} doi = {10.1515/cdbme-2023-1023} }
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Designing and Validating Magnetic Motion Sensing Approaches with a Real-time Simulation Pipeline
Authors: Johnanes Hoffmann, Christin Bald, Tobias Schmidt, Moritz Boueke, Erik Engelhardt, Karolin Krüger, Erik Elzenheimer, Clint Hansen, Walter Maetzler, Gerhard Schmidt
Publication Date: 2023-09-20
Venue: Current Directions in Biomedical Engineering
DOI: 10.1515/cdbme-2023-1114
Keywords: Ditigal twin, Localization, Magnetic methods, Magnetoelectric sensors, Motion sensing
Abstract: We introduce a comprehensive simulation pipeline based on the digital twin concept to facilitate the design and validation of magnetic motion sensing systems. Our approach addresses the hardware and software challenges of establishing setups from scratch, enabling non-contact 3D tracking of position and orientation with applications in human movement analysis.
BibTeX Citation
@inproceedings{hoffmann_designing_2023, title={Designing and Validating Magnetic Motion Sensing Approaches with a Real-time Simulation Pipeline}, author={Hoffmann, Johannes and Bald, Christin and Schmidt, Tobias and Boueke, Moritz and Engelhardt, Erik and Kr{\"u}ger, Karolin and Elzenheimer, Eric and Hansen, Clint and Maetzler, Walter and Schmidt, Gerhard}, booktitle={Current Directions in Biomedical Engineering}, volume={9}, number={1}, pages={455--458}, year={2023}, organization={De Gruyter} doi = {10.1515/cdbme-2023-1114} }
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Investigation of Converse Magnetoelectric Thin-Film Sensors for Magnetocardiography
Authors: Eric Elzenheimer, Christin Bald, Erik Engelhardt, Johannes Hoffmann, Patrick Hayes, Johan Arbustini, Andreas Bahr, Eckhard Quandt, Michael Höft, Gerhard Schmidt
Publication Date: 2022-12-10
Venue: Sensors
DOI: 10.3390/s22031018
Keywords: Application specific signal evaluation, Magnetoelectric sensors, Quantitative sensor system characterization, Sensor system performance
Abstract: We highlight metrics for quantitatively characterizing thin-film magnetoelectric (ME) sensor systems and their output signals in biomagnetism. We present an ME sensor system evaluation scheme performed under reproducible conditions, applying it to two ME sensors—a resonant ME sensor and an electrically modulated ME sensor. By introducing an application-specific capacity (ASC) as a figure of merit and comparing signal-to-noise ratios (SNRs), we demonstrate that the electrically modulated ME sensor is better suited for magnetocardiography (MCG) applications under ideal conditions. Our approach is transferable to other magnetic sensors and applications, aiding in the optimization and selection of sensor systems for medical use.
BibTeX Citation
@article{elzenheimer2022quantitative, title={Quantitative evaluation for magnetoelectric sensor systems in biomagnetic diagnostics}, author={Elzenheimer, Eric and Bald, Christin and Engelhardt, Erik and Hoffmann, Johannes and Hayes, Patrick and Arbustini, Johan and Bahr, Andreas and Quandt, Eckhard and H{\"o}ft, Michael and Schmidt, Gerhard}, journal={Sensors}, volume={22}, number={3}, pages={1018}, year={2022}, publisher={MDPI} doi={10.3390/s22031018} }
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Towards Analytically Computable Quality Classes for MCG Sensor Systems
Authors: Erik Engelhardt, Adrian Zaman, Eric Elzenheimer, Norbert Frey, Gerhard Schmidt
Publication Date: 2022-09-02
Venue: Current Directions in Biomedical Engineering
DOI: 10.1515/cdbme-2022-1176
Keywords: MCG, ECG, Sensor system characterization, Sensor System Performance, Quality Classes, Biomagnetic sensors
Abstract: We investigate the relationship between quantitative signal quality metrics—specifically signal-to-noise ratio (SNR) and application-specific capacity (ASC)—and the subjective evaluations of cardiologists using magnetocardiography (MCG) signals. By defining four quality classes and comparing noisy prototype signals, we demonstrate that it is plausible to predict qualitative assessments from these quantitative metrics, which can help manufacturers optimize MCG sensor systems and assist users in selecting the most suitable equipment for their applications.
BibTeX Citation
@inproceedings{engelhardt_towards_2022, title={Towards analytically computable quality classes for MCG sensor systems}, author={Engelhardt, Erik and Zaman, Adrian and Elzenheimer, Eric and Frey, Norbert and Schmidt, Gerhard}, booktitle={Current Directions in Biomedical Engineering}, volume={8}, number={2}, pages={691--694}, year={2022}, organization={De Gruyter} doi={10.1515/cdbme-2022-1176} } }