Advances in superconducting sensors for medical imaging and metrology: Dissertation

Research output: ThesisDissertation

Abstract

In brain imaging, two complementary but technologically contradicting techniques are magnetoencephalography (MEG) and magnetic resonance imaging (MRI). MEG examines the function of the brain by measuring very weak magnetic fields, produced as a result of neuronal activity, with sensors based on superconducting quantum interference device (SQUID). MRI employs large magnetic fields and enables imaging of the structure of matter. The recent advances in ultra-low-field (ULF) MRI have made a medical instrument incorporating MEG and ULF MRI functionalities an attractive topic of research. The contradictions become evident when comparatively high fields of ULF MRI are subjected to SQUID magnetic field sensors, degrading their performance. In this thesis, the field tolerance of the sensors was improved. Special attention was paid to sensor response recovery and operation after a magnetic pulse. A hybrid MEG-ULF MRI instrument was constructed with the aid of new sensors. The instrument operation was verified, and results indicate that including ULF MRI in a MEG device is a viable concept. In addition, a new type of magnetometer was developed, taking advantage of the nonlinear kinetic inductance of superconducting material. The experimental data, together with the theory, demonstrate a device with low noise and intrinsically high dynamic range. Furthermore, the kinetic inductance magnetometer is suitable for biomagnetic multichannel measurements, as only one amplifier is needed in the readout of multiple sensors. The simple design reduces costs in fabrication and enables higher tolerance of magnetic fields than achievable with SQUID sensors. A new superconducting transformer design is introduced as a final step. Connecting to a SQUID results in a highly sensitive current detector. The device is a candidate for closing the quantum metrology triangle (QMT) experiment, a long-standing goal in metrology. The aim of the QMT is to improve confidence in the planned revision of the SI unit system by comparing the quantum standards of current, voltage and resistance. The device was characterized for the purpose by using it as a null current detector in the simulation of a QMT experiment. Results disclose the potential of the device and provide insight into some of the practical challenges relevant to null detection.
Original languageEnglish
QualificationDoctor Degree
Awarding Institution
  • Aalto University
Supervisors/Advisors
  • Tittonen, Ilkka, Supervisor, External person
  • Hassel, Juha, Advisor
Award date12 Dec 2014
Place of PublicationEspoo
Publisher
Print ISBNs978-952-60-5955-6
Electronic ISBNs978-952-60-5956-3
Publication statusPublished - 2014
MoE publication typeG5 Doctoral dissertation (article)

Fingerprint

metrology
magnetic resonance
sensors
triangles
interference
magnetic fields
inductance
magnetometers
brain
theses
detectors
International System of Units
kinetics
closing
transformers
low noise
dynamic range
readout
confidence
amplifiers

Keywords

  • superconducting quantum interference device
  • SQUID
  • magnetoencephalography
  • MEG
  • ultra-low-field magnetic resonance imaging
  • ULF MRI
  • kinetic inductance
  • quantum metrology triangle
  • QMT
  • null detector
  • flux transformer

Cite this

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title = "Advances in superconducting sensors for medical imaging and metrology: Dissertation",
abstract = "In brain imaging, two complementary but technologically contradicting techniques are magnetoencephalography (MEG) and magnetic resonance imaging (MRI). MEG examines the function of the brain by measuring very weak magnetic fields, produced as a result of neuronal activity, with sensors based on superconducting quantum interference device (SQUID). MRI employs large magnetic fields and enables imaging of the structure of matter. The recent advances in ultra-low-field (ULF) MRI have made a medical instrument incorporating MEG and ULF MRI functionalities an attractive topic of research. The contradictions become evident when comparatively high fields of ULF MRI are subjected to SQUID magnetic field sensors, degrading their performance. In this thesis, the field tolerance of the sensors was improved. Special attention was paid to sensor response recovery and operation after a magnetic pulse. A hybrid MEG-ULF MRI instrument was constructed with the aid of new sensors. The instrument operation was verified, and results indicate that including ULF MRI in a MEG device is a viable concept. In addition, a new type of magnetometer was developed, taking advantage of the nonlinear kinetic inductance of superconducting material. The experimental data, together with the theory, demonstrate a device with low noise and intrinsically high dynamic range. Furthermore, the kinetic inductance magnetometer is suitable for biomagnetic multichannel measurements, as only one amplifier is needed in the readout of multiple sensors. The simple design reduces costs in fabrication and enables higher tolerance of magnetic fields than achievable with SQUID sensors. A new superconducting transformer design is introduced as a final step. Connecting to a SQUID results in a highly sensitive current detector. The device is a candidate for closing the quantum metrology triangle (QMT) experiment, a long-standing goal in metrology. The aim of the QMT is to improve confidence in the planned revision of the SI unit system by comparing the quantum standards of current, voltage and resistance. The device was characterized for the purpose by using it as a null current detector in the simulation of a QMT experiment. Results disclose the potential of the device and provide insight into some of the practical challenges relevant to null detection.",
keywords = "superconducting quantum interference device, SQUID, magnetoencephalography, MEG, ultra-low-field magnetic resonance imaging, ULF MRI, kinetic inductance, quantum metrology triangle, QMT, null detector, flux transformer",
author = "Juho Luomahaara",
note = "76 p. + app. 45",
year = "2014",
language = "English",
isbn = "978-952-60-5955-6",
series = "Aalto University Publication Series: Doctoral Dissertations",
publisher = "Aalto University",
number = "182",
address = "Finland",
school = "Aalto University",

}

Advances in superconducting sensors for medical imaging and metrology : Dissertation. / Luomahaara, Juho.

Espoo : Aalto University, 2014. 121 p.

Research output: ThesisDissertation

TY - THES

T1 - Advances in superconducting sensors for medical imaging and metrology

T2 - Dissertation

AU - Luomahaara, Juho

N1 - 76 p. + app. 45

PY - 2014

Y1 - 2014

N2 - In brain imaging, two complementary but technologically contradicting techniques are magnetoencephalography (MEG) and magnetic resonance imaging (MRI). MEG examines the function of the brain by measuring very weak magnetic fields, produced as a result of neuronal activity, with sensors based on superconducting quantum interference device (SQUID). MRI employs large magnetic fields and enables imaging of the structure of matter. The recent advances in ultra-low-field (ULF) MRI have made a medical instrument incorporating MEG and ULF MRI functionalities an attractive topic of research. The contradictions become evident when comparatively high fields of ULF MRI are subjected to SQUID magnetic field sensors, degrading their performance. In this thesis, the field tolerance of the sensors was improved. Special attention was paid to sensor response recovery and operation after a magnetic pulse. A hybrid MEG-ULF MRI instrument was constructed with the aid of new sensors. The instrument operation was verified, and results indicate that including ULF MRI in a MEG device is a viable concept. In addition, a new type of magnetometer was developed, taking advantage of the nonlinear kinetic inductance of superconducting material. The experimental data, together with the theory, demonstrate a device with low noise and intrinsically high dynamic range. Furthermore, the kinetic inductance magnetometer is suitable for biomagnetic multichannel measurements, as only one amplifier is needed in the readout of multiple sensors. The simple design reduces costs in fabrication and enables higher tolerance of magnetic fields than achievable with SQUID sensors. A new superconducting transformer design is introduced as a final step. Connecting to a SQUID results in a highly sensitive current detector. The device is a candidate for closing the quantum metrology triangle (QMT) experiment, a long-standing goal in metrology. The aim of the QMT is to improve confidence in the planned revision of the SI unit system by comparing the quantum standards of current, voltage and resistance. The device was characterized for the purpose by using it as a null current detector in the simulation of a QMT experiment. Results disclose the potential of the device and provide insight into some of the practical challenges relevant to null detection.

AB - In brain imaging, two complementary but technologically contradicting techniques are magnetoencephalography (MEG) and magnetic resonance imaging (MRI). MEG examines the function of the brain by measuring very weak magnetic fields, produced as a result of neuronal activity, with sensors based on superconducting quantum interference device (SQUID). MRI employs large magnetic fields and enables imaging of the structure of matter. The recent advances in ultra-low-field (ULF) MRI have made a medical instrument incorporating MEG and ULF MRI functionalities an attractive topic of research. The contradictions become evident when comparatively high fields of ULF MRI are subjected to SQUID magnetic field sensors, degrading their performance. In this thesis, the field tolerance of the sensors was improved. Special attention was paid to sensor response recovery and operation after a magnetic pulse. A hybrid MEG-ULF MRI instrument was constructed with the aid of new sensors. The instrument operation was verified, and results indicate that including ULF MRI in a MEG device is a viable concept. In addition, a new type of magnetometer was developed, taking advantage of the nonlinear kinetic inductance of superconducting material. The experimental data, together with the theory, demonstrate a device with low noise and intrinsically high dynamic range. Furthermore, the kinetic inductance magnetometer is suitable for biomagnetic multichannel measurements, as only one amplifier is needed in the readout of multiple sensors. The simple design reduces costs in fabrication and enables higher tolerance of magnetic fields than achievable with SQUID sensors. A new superconducting transformer design is introduced as a final step. Connecting to a SQUID results in a highly sensitive current detector. The device is a candidate for closing the quantum metrology triangle (QMT) experiment, a long-standing goal in metrology. The aim of the QMT is to improve confidence in the planned revision of the SI unit system by comparing the quantum standards of current, voltage and resistance. The device was characterized for the purpose by using it as a null current detector in the simulation of a QMT experiment. Results disclose the potential of the device and provide insight into some of the practical challenges relevant to null detection.

KW - superconducting quantum interference device

KW - SQUID

KW - magnetoencephalography

KW - MEG

KW - ultra-low-field magnetic resonance imaging

KW - ULF MRI

KW - kinetic inductance

KW - quantum metrology triangle

KW - QMT

KW - null detector

KW - flux transformer

M3 - Dissertation

SN - 978-952-60-5955-6

T3 - Aalto University Publication Series: Doctoral Dissertations

PB - Aalto University

CY - Espoo

ER -