Advances in superconducting sensors for medical imaging and metrology

Juho Luomahaara

Advances in superconducting sensors for medical imaging and metrology

Julkaisun otsikon käännös: Edistysaskelia suprajohtavien antureiden kehityksessä lääketieteellisen kuvantamisen ja metrologian tarpeisiin

Juho Luomahaara

Tutkimustuotos: Doctoral Thesis › Collection of Articles

Abstrakti

Aivokuvantamisessa kaksi toisiaan täydentävää, mutta teknisesti vastakkaista menetelmää ovat magnetoenkefalografia (MEG) ja magneettikuvaus (MRI). MEG tutkii aivojen toimintaa mittaamalla suprajohtavaan kvantti-interferenssilaitteeseen (SQUID) perustuvilla antureilla hermosignaalien seurauksena syntyviä, erittäin heikkoja magneettikenttiä. Korkeiden magneettikenttien käyttö MRI:ssä mahdollistaa materiaalin rakenteen kuvantamisen. Ultramatalan kentän (ULF) MRI:ssä tapahtuneen kehityksen seurauksena MEG:n ja ULF MRI:n yhdistämisestä yhdeksi mittalaitteeksi onkin tullut kiinnostava tutkimuskohde. Menetelmien ristiriitaiset vaatimukset tulevat esille, kun ULF MRI:n verrattain korkeat magneettikentät kohdistetaan SQUID-magneettikenttäantureihin, mikä heikentää niiden suorituskykyä. Tässä väitöskirjassa antureiden kenttäsietoisuutta parannettiin kiinnittämällä erityistä huomiota niiden toipumiseen ja toimintaan magneettipulssin jälkeen. Kehitettyjen antureiden avulla työssä rakennettiin yhdistetty MEG-ULF MRI -laite. Laitteen toiminta verifioitiin ja tulokset osoittavat, että ULF MRI -toiminnallisuus tuo lisäarvoa MEG-laitteeseen. Väitöskirjassa kehitettiin myös uudenlainen magneettikenttäanturi käyttäen hyväksi kineettisen induktanssin epälineaarisuutta suprajohtavassa materiaalissa. Kokeelliset tulokset yhdessä kehitetyn teorian kanssa osoittavat, että laitteella on matala kohinataso ja luontaisesti laaja dynaaminen alue. Lisäksi kineettisen induktanssin magnetometri soveltuu hyvin monen kanavan biomagneettisiin mittauksiin, sillä usean anturin luenta voidaan hoitaa yhdellä vahvistimella. Laitteen yksinkertaisuus vähentää valmistuskustannuksia ja mahdollistaa SQUID-antureita paremman magneettikenttäsietoisuuden. Lopuksi työssä esitellään uudenlainen suprajohtava muuntaja. Kytkemällä se SQUID-anturiin saadaan aikaan erittäin herkkä virtamittari. Laitetta voidaan käyttää kvanttimetrologiakolmiokokeen (QMT) sulkemiseen, joka on yksi metrologian pitkäaikaisista tavoitteista. QMT:n tarkoituksena on kasvattaa luottamusta suunniteltuun SI-yksikköjärjestelmäuudistukseen vertaamalla virran, jännitteen ja vastuksen kvanttinormaaleja toisiinsa. Laite karakterisoitiin tarkoitusta varten käyttämällä sitä nollailmaisimena QMT-kokeen simuloinnissa. Tulokset osoittavat kehitetyn laitteen potentiaalin ja antavat yksityiskohtaista tietoa nollailmaisuun liittyvistä käytännön haasteista.

Julkaisun otsikon käännös	Edistysaskelia suprajohtavien antureiden kehityksessä lääketieteellisen kuvantamisen ja metrologian tarpeisiin
Alkuperäiskieli	Englanti
Pätevyys	Tohtorintutkinto
Myöntävä instituutio	Aalto-yliopisto
Valvoja/neuvonantaja	Tittonen, Ilkka, Vastuuprofessori Hassel, Juha, Ohjaaja, Ulkoinen henkilö
Kustantaja	Aalto University
Painoksen ISBN	978-952-60-5955-6
Sähköinen ISBN	978-952-60-5956-3
Tila	Julkaistu - 2014
OKM-julkaisutyyppi	G5 Artikkeliväitöskirja

Tutkimusalat

suprajohtava kvantti-interferenssilaite
magnetoenkefalografia
ultramatalan kentän magneettikuvaus
kineettinen induktanssi
kvanttimetrologiakolmio
nollailmaisin
vuomuuntaja

Pääsy asiakirjaan

http://urn.fi/URN:ISBN:978-952-60-5956-3

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@phdthesis{b60551e3e03e4654bf1687a48c50a371,

title = "Advances in superconducting sensors for medical imaging and metrology",

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, suprajohtava kvantti-interferenssilaite, magnetoenkefalografia, ultramatalan kent{\"a}n magneettikuvaus, kineettinen induktanssi, kvanttimetrologiakolmio, nollailmaisin, vuomuuntaja, 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",

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",

}

TY - BOOK

T1 - Advances in superconducting sensors for medical imaging and metrology

AU - Luomahaara, Juho

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

KW - suprajohtava kvantti-interferenssilaite

KW - magnetoenkefalografia

KW - ultramatalan kentän magneettikuvaus

KW - kineettinen induktanssi

KW - kvanttimetrologiakolmio

KW - nollailmaisin

KW - vuomuuntaja

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 - Doctoral Thesis

SN - 978-952-60-5955-6

T3 - Aalto University publication series DOCTORAL DISSERTATIONS

PB - Aalto University

ER -

Advances in superconducting sensors for medical imaging and metrology

Abstrakti

Tutkimusalat

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