Flexible High Performance Magnetic Field Sensors: On-Scalp Magnetoencephalography and Other Applications

Description

This contributed volume reviews the latest advances in all the new technologies currently developed for MagnetoEncephaloGraphy (MEG) recordings, as well as sensor technologies and integrated sensor arrays for on-scalp MEG. The book gives an account of the first MEG imaging studies and explores the new field of feasible, experimental paradigms of on-scalp MEG. This is an ideal book for engineers, researchers, and students in the neurosciences interested in MEG imaging.  Preface Contents About the Editors Part I OPM and System Developments 1 Optically Pumped Magnetometers for Biomagnetic Measurements 1.1 Introduction 1.2 General Features of Atomic Magnetometer Operation 1.3 Sensitivity of Atomic Magnetometers 1.4 Alkali-Metal Atomic Magnetometers 1.4.1 Spin-Exchange Relaxation-Free Alkali-Metal Magnetometers 1.5 Practical Challenges in Operation of Atomic Magnetometers 1.6 Conclusions References 2 Optically Pumped Magnetometers Compatible with Large Transient Magnetic Fields 2.1 Introduction 2.1.1 Brief Introduction to SERF OPMs 2.2 Methods for Stable Operation in a Noisy Environment 2.2.1 Closed-Loop Mode 2.2.2 Magnetic Gradiometry 2.3 Transcranial Magnetic Stimulation 2.4 Conclusion References 3 Small Animal Biomagnetism Applications 3.1 Introduction 3.1.1 High Sensitivity Optically Pumped Magnetometers for Biomagnetic Recordings 3.1.2 Why Biomagnetic Recordings on Small Animals? 3.1.3 Examples of Animal Biomagnetic Recordings 3.1.4 Ethics and Legislation 3.2 Optically Pumped Magnetometer 3.3 Biomagnetic Recordings 3.3.1 Detection of Nerve Impulses 3.3.2 Cardiology Applications 3.3.3 Towards Imaging the Electrical Conductivity of the Heart 3.4 Conclusions References 4 Supine OPM-MEG in Multilayer Cylindrical Shield 4.1 Introduction 4.2 Multichannel OPM Array 4.2.1 All-Optical OPM and Sensitivity 4.2.2 Multichannel Control System 4.3 Multilayer Cylindrical Shield 4.3.1 Magnetic Shielding for MEG 4.3.2 Finite Element Method 4.3.3 Performance of a Four-Layer Cylindrical Shield 4.4 Sensor-to-Brain Co-registration and Source Imaging 4.4.1 Sensor Localization and Co-registration 4.4.2 Multichannel Detection and Source Imaging 4.5 Summary and Future Work References 5 Ambulatory MEG Arrays 5.1 Introduction 5.2 Background 5.3 OPM Arrays 5.4 OPM Helmet 5.5 Sensor Connections and Cable Management 5.6 Triaxial Operation 5.7 Electronics Miniaturization 5.8 System Architecture 5.9 Discussion and Future Outlook References Part II MEG Applications 6 Tri-axial Helium-4 Optically Pumped Magnetometers for MEG 6.1 Introduction 6.2 Helium Magnetometers for Space Exploration 6.3 Helium Magnetometers Transfer to Biomedical Imaging 6.3.1 Optically Pumped Magnetometers Based on Atomic Alignment 6.3.2 The Evolution of Aligned States in Parametric Resonance Magnetometers 6.4 First Demonstration of MCG 6.4.1 Phantom Measurement 6.4.2 MCG Measurements on Healthy Volunteers 6.5 First Demonstration of MEG 6.5.1 Simulated MEG Signals from a Brain Phantom 6.5.2 MEG Recordings on a Healthy Subject 6.6 An Array of Second-Generation Helium Magnetometers 6.6.1 Probe Configuration 6.6.2 Sensitivity and Bandwidth in Open-Loop Operation 6.6.3 Closed-Loop Operation: Principle and Intrinsic Noise 6.6.4 Correcting the Cross-Talks in Closed-Loop Operation 6.7 Alternative Magnetometer Configurations Based on Aligned Ensembles of Metastable Helium-4 6.7.1 An All-Optical Magnetometer Based on Hanle Effect on an Aligned Atomic Ensemble 6.7.2 A Parametric Resonance Magnetometer Based Both on Atomic Orientation and Alignment 6.8 Conclusion References 7 Person-Sized Magnetoencephalography Systems with Optically Pumped Magnetometers 7.1 Introduction 7.2 Magnetic Shielding 7.2.1 Design of Our Person-Sized Shield 7.2.2 Magnetic Field Control Within the Shield 7.3 The Optically Pumped Magnetometer 7.3.1 OPM Design 7.3.2 Importance of Magnetic Field Control 7.3.3 The OPM-MEG System 7.3.4 Laser System 7.3.5 Temperature Controller 7.3.6 Signal Detection 7.3.7 Magnetic Field Generation 7.4 Testing with Human Subjects 7.4.1 Stimuli Presentation 7.4.2 Signal Processing Pipeline 7.4.2.1 Magnetoencephalography Data Processing 7.4.2.2 Constructing the Forward Model 7.4.2.3 Neuronal Current Source Localization 7.4.3 Magnetoencephalography Results 7.5 Conclusion References 8 On-scalp MEG with High-Tc SQUIDs 8.1 Introduction 8.2 High-Tc SQUID Sensitivity 8.3 Spatial Sampling Theory: Maximizing the On-scalp Benefit 8.4 System Design Considerations 8.5 Technical Developments Toward Practical On-scalp MEG Measurements 8.6 Experimental Demonstrations of High-Tc SQUID-based On-scalp MEG Advantages 8.7 Conclusions and Future Prospects References 9 Fiber-Coupled OPM in Purely Coil-Shielded Environment 9.1 Introduction 9.2 Bell-Bloom Atomic Magnetometer 9.3 Active Magnetic Field Stabilization 9.4 Unshielded MEG Measurements 9.5 Conclusions and Outlook References 10 SERF-OPM Usability for MEG in Two-Layer-Shielded Rooms 10.1 Introduction 10.2 SERF-OPM-MEG Setup in a Two-Layer Actively Shielded Room 10.3 SERF-OPM Signal Characteristics in Empty Room 10.4 OPM-MEG Feasibility Demonstration with Subjects 10.5 Source Localization Comparison of OPM- and SQUID-MEG Data 10.6 Discussion and Conclusion References 11 Turning OPM-MEG into a Wearable Technology 11.1 Introduction 11.1.1 An Overview of Conventional MEG 11.1.2 Why OPMs Are the Stand-Out Replacement 11.2 Technical Challenges 11.2.1 What an OPM for MEG Should Look Like 11.2.1.1 Single Axis vs Triaxial 11.2.1.2 Magnetometer vs. Gradiometer 11.2.1.3 Nascent OPM Designs 11.2.2 Designing OPM Sensor Arrays for MEG 11.2.2.1 Region-Specific OPM-MEG Arrays 11.2.2.2 Fixed or Wearable Arrays 11.2.2.3 3D-Printed Individual Scanner Casts 11.2.2.4 Generic Caps and Helmets 11.2.2.5 Crosstalk 11.2.3 Suppressing Background Magnetic Fields 11.2.3.1 Magnetically Shielded Environments 11.2.3.2 Using Coils to Null the Static Remnant Magnetic Field 11.2.3.3 Nulling Dynamic Magnetic Fields 11.3 Applications 11.3.1 Novel Paradigms 11.3.2 New Subject Cohorts 11.3.3 Creative Sensor Placement 11.4 Conclusion and Future Outlook References Part III MCG, MRX, and Other Applications 12 OPM Gradiometer for Magnetorelaxometry 12.1 Introduction 12.1.1 Magnetic Nanoparticles and Relaxation 12.1.2 Magnetorelaxometry Principles 12.1.3 Application of MNP Relaxation to Biological Processes 12.2 Development of a System for Magnetorelaxometry in Samples and Small Animals 12.3 State of the Art and Perspectives 12.4 Conclusion References 13 Unshielded High-Bandwidth Magnetorelaxometry of Magnetic Nanoparticles with Optically PumpedMagnetometers 13.1 Introduction 13.2 The Need for High Bandwidth in MRX 13.3 OPM Operation Modes for High Bandwidth and Unshielded Operation 13.4 MRX with Feedback-Controlled OPMs in Weakly Shielded Environments 13.5 Free Spin Precession OPM 13.6 Unshielded MRX with a Commercially Available Free Spin Precession OPM 13.7 Conclusion and Outlook References 14 Adult Magnetocardiography: Principles and Clinical Practice 14.1 Introduction 14.2 Implementation of OPM-MCG 14.2.1 Hardware Overview and Common Practice 14.2.2 Data Analysis 14.3 Adult Magnetocardiography in Clinical Practice: A Review of SQUID and OPM Paradigms and Analysis References 15 Fetal Magnetocardiography with OPMs 15.1 Overview of fMCG 15.2 fMCG System Design Considerations 15.2.1 fMCG Signal Characteristics 15.2.2 fMCG System Components 15.2.2.1 Magnetic Sensors 15.2.2.2 Magnetic Shielding 15.2.2.3 Signal Processing Techniques 15.3 A Prototype OPM fMCG System 15.3.1 Person-Sized Shield 15.3.2 OPM Sensor Array 15.3.3 Performance Assessment 15.3.3.1 Signal-to-Noise Ratio 15.3.3.2 Diagnostic Information 15.3.3.3 Subject Comfort 15.4 Conclusions 15.5 Future Directions References 16 Emerging MR Sensors for Biomagnetic Measurements 16.1 Magnetoresistive Device-Based Magnetic Flux Sensors 16.2 Calibration of Sensor Array 16.3 Magnetocardiographic Measurements by MR Sensors 16.4 Magnetoneurographic Measurements by MR Sensors 16.5 Conclusion References Index