Abstract
To measure weak magnetoencephalography (MEG) signals, two basic technical requirements are sensitive magnetic sensors and reduction of environmental noises. Until now, magnetic field sensors based on superconducting quantum interference devices (SQUIDs) made from low-temperature superconductors are the main sensors used for measuring MEG signals. For effective reduction of strong environmental magnetic noise, combination of magnetic shielding and gradiometers (hardware and/or software) is typically used. Since SQUIDs are very sensitive devices, care should be taken in handling them and in using them for multichannel MEG sensor arrays. Electrostatic shocks or strong magnetic fields can damage the normal operation of SQUIDs. Cooling of the SQUIDs needs a helmet-shaped dewar which should provide reliable operation for longer than 1 year in vacuum tightness, and boil-off of the liquid He should be optimized to have a refill interval longer than 1 week. For economic MEG systems, the SQUID array should be simple in the manufacturing process, and the structure of the sensor array should be compact. For the MEG system to be operated easily, the process for signal acquisition and signal processing devices needs to be simple, using a single personal computer. A magnetically shielded room (MSR) is mandatory for urban hospitals or downtown laboratory environments. Considering the high cost of magnetic alloy used in the construction of a MSR, optimization and cost-effective construction are needed. Even if the MEG measurements are done in a quiet or well-shielded environment, the signal-to-noise ratio of MEG signals is not sufficiently high, and signal processing is needed to remove some artifacts generated from the human body. This chapter presents basic technical issues for MEG instrumentation, especially in fabricating and operating economic MEG systems. In the later part of this chapter, atomic magnetometers for future non-cryogenic MEG systems and brain magnetic resonance based on low-field nuclear magnetic resonance for visualizing brain functional activity are described.
This is a preview of subscription content, log in via an institution to check access.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
References
Adelerhof DJ, Nijstad H, Flokstra J, Rogalla H (1994) (Double) relaxation oscillation SQUIDs with high flux-to-voltage transfer: simulations and experiments. J Appl Phys 76:3875–3886
Cardoso JF (1999) High-order contrasts for independent component analysis. Neural Comput 11(1):157–192
Del Gratta C, Pizzella V, Tecchio F, Romani GL (2001) Magnetoencephalography—a noninvasive brain imaging method with 1 ms time resolution. Rep Prog Phys 64:1759–1814
Dössel O, David B, Fuchs M, Krüger J, Lüdeke KM, Wischmann HA (1993) A modular 31-channel SQUID system for biomagnetic measurements. IEEE Trans Appl Supercond 3:1883–1886
Drung D (1996) SQUID sensors. In: Weinstock H (ed) Fundamentals, fabrication and applications. Kluwer, Dordrecht, pp 63–116
Drung D, Mück M (2004) SQUID electronics. In: Clarke J, Braginski AI (eds) The SQUID handbook. Wiley, Weinheim, pp 569–578
Erné SN (1983) Shielded rooms. In: Williamson SJ, Romani GL, Kaufman MI (eds) Biomagnetism, an interdisplinary approach. Plenum Press, New York, pp 85–135
Faley MI, Poppe U, Dunin-Borkowski RE, Schiek M, Boers F, Chocholacs H, Dammers J, Eich E, Shah NJ, Ermakov AB, Slobodchikov VY, Maslennikov YV, Koshelets VP (2013) High-Tc DC SQUIDS for magnetoencephalography. IEEE Trans Appl Supercond 23(3):1600705
Hämäläinen M, Hari R, Ilmoniemi RJ, Knuutila J, Lounasmaa OV (1993) Magnetoencephalography. Theory, instrumentation and applications to the noninvasive study of human brain function. Rev Mod Phys 65:413–497
Kelhä VO, Pukki JM, Peltonen RS, Penttinen AJ, Ilmoniemi RJ, Heino JJ (1982) Design, construction, and performance of a large-volume magnetic shield. IEEE Trans Magn 18(1):260–270
Ketchen MB (1987) Integrated thin-film dc SQUID sensors. IEEE Trans Magn 23:1650–1657
Kim K (2012) Toward cardiac electrophysiological mapping based on micro-Tesla NMR: a novel modality for localizing the cardiac reentry. Am Inst Phys Adv 2(2):022156
Kim K, Lee YH, Kwon H, Kim JM, Park YK, Kim IS (2004) Correction in the principal component elimination method for neuromagnetic evoked field measurements. J Korean Phys Soc 44(4):980–986
Kim K, Xia H, Lee SK, Romalis M (2008) Development of a wide-coverage atomic brain magnetometer system. In: Proceedings of 16th international conference on biomagnetism, Vancouver, BC, Canada, pp 229–232
Kim K, Begus S, Xia H, Lee SK, Jazbinsek V, Trontelj Z, Romalis MV (2014a) Multi-channel atomic magnetometer for magnetoencephalography: A configuration study. Neuroimage 89:143–151
Kim K, Lee SJ, Kang CS, Hwang SM, Lee YH, Yu KK (2014b) Toward a brain functional connectivity mapping modality by simultaneous imaging of coherent brainwaves. Neuroimage 91:63–69
Knuutila J (2007) Instrumentation development: from MEG recording to functional mapping. Int Congr Ser 1300:7–10
Lee YH, Kwon H, Kim JM, Park YK, Park JC (1999) Noise characteristics of double relaxation oscillation superconducting quantum interference devices with reference junction. Supercond Sci Technol 12:943–945
Lee YH, Kwon H, Kim JM, Kim K, Kim IS, Park YK (2005) Double relaxation oscillation SQUID system for biomagnetic multichannel measurements. IEICE Trans Electron E88-C:168–174
Lee YH, Yu KK, Kwon H, Kim JM, Kim K, Park YK, Yang HC, Chen KL, Yang SY, Horng HE (2009) A whole-head magnetoencephalography system with compact axial gradiometer structure. Supercond Sci Technol 22:045023
Nowak H (1998) Biomagnetism. In: Andrä W, Nowak H (eds) Magnetism in medicine. Wiley, Berlin, pp 85–135
Parkkonen L (2010) Instrumentation and data processing. In: Hansen PC, Kringelbach ML, Salmelin R (eds) MEG: an introduction to methods. Oxford University Press, Oxford, pp 24–64
Pizzella V, Della Penna S, Del Gratta C, Romani GL (2001) SQUID systems for biomagnetic imaging. Supercond Sci Technol 14:R79–R114
Sander TH, Preusser J, Mhaskar R, Kitching J, Trahms L, Knappe S (2012) Magnetoencephalography with a chip-scale atomic magnetometer. Biomed Opt Express 3(5):981–990
Sata K, Yoshida T, Fujimoto S, Miyahara S, Kang YM (1999) A Cryocooled helmet-shaped MEG measurement system. In: Proceeding of international superconductive electronics conference, pp 406–408
Sullivan GW, Lewis PS, George JS, Flynn ER (1989) A magnetic shielded room designed for magnetoencephalography. Rev Sci Instrum 60(4):765–770
Taulu S, Kajola M, Simola J (2004) Suppression of interference and artifacts by the signal space separation method. Brain Topogr 16(4):269–275
ter Brake HJM, Fleuren FH, Ulfman JA, Flokstra J (1986) Elimination of flux-transformer crosstalk in multichannel SQUID magnetometers. Cryogenics 26:667–670
ter Brake HJM, Flokstra J, Houwman EP, Veldhuis D, Jaszczuk W, Stammis R, van Ancum GK, Rogalla H (1992) On the SQUID-module for the UT multichannel neuromagnetometer. In: Superconducting devices and their applications. Springer, Berlin 521–524
Uusitalo MA, Ilmoniemi RJ (1997) Signal-space projection method for separating MEG or EEG into components. Med Biol Eng Comput 35:135–140
Vrba J, Robinson SE (2001) Signal processing in magnetoencephalography. Methods 25:249–271
Vrba J, Robinson SE (2002) SQUID sensor array configurations for magnetoencephalography applications. Supercond Sci Technol 15:R51–R89
Author information
Authors and Affiliations
Corresponding authors
Editor information
Editors and Affiliations
Section Editor information
Rights and permissions
Copyright information
© 2019 Springer Nature Switzerland AG
About this entry
Cite this entry
Lee, YH., Kim, K. (2019). Instrumentation for Measuring MEG Signals. In: Supek, S., Aine, C. (eds) Magnetoencephalography. Springer, Cham. https://doi.org/10.1007/978-3-030-00087-5_1
Download citation
DOI: https://doi.org/10.1007/978-3-030-00087-5_1
Published:
Publisher Name: Springer, Cham
Print ISBN: 978-3-030-00086-8
Online ISBN: 978-3-030-00087-5
eBook Packages: Biomedical and Life SciencesReference Module Biomedical and Life Sciences