Aivon Oy

Espoo, Finland
Espoo, Finland
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Grant
Agency: European Commission | Branch: FP7 | Program: CP-FP | Phase: HEALTH-2007-1.2-1 | Award Amount: 6.85M | Year: 2008

We will develop and validate hybrid magnetoencephalography (MEG) and magnetic resonance imaging (MRI) technology that will allow simultaneous structural (MRI) and functional (MEG) imaging of the human brain. MEG is a non-invasive 3D functional imaging with a high temporal resolution compared to other functional imaging but often suffers from a precise structural localization which will be solved by the dual modality approach of the MEGMRI hybrid scanner. In parallel, low field MRI, a new very promising alternative to conventional high field MRI will provide enhanced image contrast in certain applications, improved geometric accuracy, improve safety (for patient with pacemakers and other implants, for pregnant women, for infants), and reduce costs. These new opportunities are based on recent advances in ultra-sensitive magnetic sensors. Superconducting magnetometers based on quantum interference devices (SQUIDs) have been recently used to provide 2D-MRI images at very low fields by two US teams. In parallel, a new type of magnetometer, called mixed sensor, based on spin electronics devices, has been developed within our consortium and used for low-field NMR. The first part of the project will be focused on sensor optimization, and low-field MRI development. This covers the development of field-tolerant SQUIDs and optimized mixed sensors and 3D-MRI low-field hardware and software development. The second part of the project will be devoted to a prototype building with the best kind of sensor and extensive preclinical validation, covering major brain disorders for adults and children. The consortium of MEGMRI has the necessary skills to perform all the tasks: sensor developers, MRI experts, MEG developers and clinical validators. It contains 13 partners from 5 countries including 3 SMEs and one large medical device manufacturer.


Luomahaara J.,VTT Technical Research Center of Finland | Vesanen P.T.,Aalto University | Penttila J.,Aivon Oy | Nieminen J.O.,Aalto University | And 7 more authors.
Superconductor Science and Technology | Year: 2011

Flux trapping and random flux movement are common problems in superconducting thin-film devices. Ultrasensitive magnetic field sensors based on superconducting quantum interference devices (SQUIDs) coupled to large pickup coils are especially vulnerable to strong external fields. The issue has become particularly relevant with the introduction of SQUID-based ultra-low-field (ULF) nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) techniques. In this paper, we study the constraints of thin-film-based magnetometers and gradiometers as exposed to magnetic field sequences of ULF MRI. In particular, we address issues such as response recovery, transient noise, magnetization and behaviour under shielded room conditions after prepolarization. As a result, we demonstrate sensors that are suitable for a combined multi-channel magnetoencephalography (MEG) and MRI imaging system. © 2011 IOP Publishing Ltd.


Nieminen J.O.,Aalto University | Vesanen P.T.,Aalto University | Zevenhoven K.C.J.,Aalto University | Dabek J.,Aalto University | And 4 more authors.
Journal of Magnetic Resonance | Year: 2011

In ultra-low-field magnetic resonance imaging (ULF MRI), superconductive sensors are used to detect MRI signals typically in fields on the order of 10-100 μT. Despite the highly sensitive detectors, it is necessary to prepolarize the sample in a stronger magnetic field on the order of 10-100 mT, which has to be switched off rapidly in a few milliseconds before signal acquisition. In addition, external magnetic interference is commonly reduced by situating the ULF-MRI system inside a magnetically shielded room (MSR). With typical dipolar polarizing coil designs, the stray field induces strong eddy currents in the conductive layers of the MSR. These eddy currents cause significant secondary magnetic fields that may distort the spin dynamics of the sample, exceed the dynamic range of the sensors, and prevent simultaneous magnetoencephalography and MRI acquisitions. In this paper, we describe a method to design self-shielded polarizing coils for ULF MRI. The experimental results show that with a simple self-shielded polarizing coil, the magnetic fields caused by the eddy currents are largely reduced. With the presented shielding technique, ULF-MRI devices can utilize stronger and spatially broader polarizing fields than achievable with unshielded polarizing coils. © 2011 Elsevier Inc. All rights reserved.


Vesanen P.T.,Aalto University | Nieminen J.O.,Aalto University | Zevenhoven K.C.J.,Aalto University | Dabek J.,Aalto University | And 10 more authors.
Magnetic Resonance in Medicine | Year: 2013

Ultra-low-field MRI uses microtesla fields for signal encoding and sensitive superconducting quantum interference devices for signal detection. Similarly, modern magnetoencephalography (MEG) systems use arrays comprising hundreds of superconducting quantum interference device channels to measure the magnetic field generated by neuronal activity. In this article, hybrid MEG-MRI instrumentation based on a commercial whole-head MEG device is described. The combination of ultra-low-field MRI and MEG in a single device is expected to significantly reduce coregistration errors between the two modalities, to simplify MEG analysis, and to improve MEG localization accuracy. The sensor solutions, MRI coils (including a superconducting polarizing coil), an optimized pulse sequence, and a reconstruction method suitable for hybrid MEG-MRI measurements are described. The performance of the device is demonstrated by presenting ultra-low-field-MR images and MEG recordings that are compared with data obtained with a 3T scanner and a commercial MEG device. © 2012 Wiley Periodicals, Inc.


Hahtela O.M.,Center for Metrology and Accreditation | Meschke M.,Aalto University | Savin A.,Aalto University | Gunnarsson D.,VTT Technical Research Center of Finland | And 6 more authors.
AIP Conference Proceedings | Year: 2013

Coulomb blockade thermometry (CBT) has proven to be a feasible method for primary thermometry in every day laboratory use at cryogenic temperatures from ca. 10 mK to a few tens of kelvins. The operation of CBT is based on single electron charging effects in normal metal tunnel junctions. In this paper, we discuss the typical error sources and uncertainty components that limit the present absolute accuracy of the CBT measurements to the level of about 1 % in the optimum temperature range. Identifying the influence of different uncertainty sources is a good starting point for improving the measurement accuracy to the level that would allow the CBT to be more widely used in high-precision low temperature metrological applications and for realizing thermodynamic temperature in accordance to the upcoming new definition of kelvin. © 2013 AIP Publishing LLC.


Bradley D.I.,Lancaster University | George R.E.,Lancaster University | Gunnarsson D.,VTT Technical Research Center of Finland | Haley R.P.,Lancaster University | And 8 more authors.
Nature Communications | Year: 2016

Cooling nanoelectronic structures to millikelvin temperatures presents extreme challenges in maintaining thermal contact between the electrons in the device and an external cold bath. It is typically found that when nanoscale devices are cooled to ∼ 10mK the electrons are significantly overheated. Here we report the cooling of electrons in nanoelectronic Coulomb blockade thermometers below 4 mK. The low operating temperature is attributed to an optimized design that incorporates cooling fins with a high electron-phonon coupling and on-chip electronic filters, combined with low-noise electronic measurements. By immersing a Coulomb blockade thermometer in the 3He/4He refrigerant of a dilution refrigerator, we measure a lowest electron temperature of 3.7mK and a trend to a saturated electron temperature approaching 3 mK. This work demonstrates how nanoelectronic samples can be cooled further into the low-millikelvin range.


Beev N.,VTT Technical Research Center of Finland | Kiviranta M.,VTT Technical Research Center of Finland | Van Der Kuur J.,SRON Netherlands Institute for Space Research | Bruijn M.,SRON Netherlands Institute for Space Research | And 6 more authors.
Journal of Physics: Conference Series | Year: 2014

We have demonstrated the operation of a 12-channel Beyer-style SQUID-based time domain multiplexer. It was manufactured using a fabrication process that is cross-compatible between VTT and IPHT-Jena. The multiplexer consists of twelve 12-SQUID series arrays, each shunted by a Zappe-style interferometer array acting as a flux-controlled superconducting/normal conducting switch. By keeping all switches but one in the superconducting state, it is possible to select one active readout channel at a time. A flux feedback coil common to all SQUID arrays allows realization of a flux-locked loop. We present characteristics of the multiplexer and measurement data from experiments with a 25-pixel X-ray calorimeter array operated at T < 100 mK in a dilution refrigerator. © Published under licence by IOP Publishing Ltd.


Roschier L.,Aivon Oy | Gunnarsson D.,VTT Technical Research Center of Finland | Meschke M.,Aalto University | Savin A.,Aalto University | And 2 more authors.
Journal of Physics: Conference Series | Year: 2012

Coulomb Blockade Thermometer (CBT) is a primary thermometer based on electric conductance of normal tunnel junction arrays. One limitation for CBT use at the lowest temperatures has been due to environmental noise heating. To improve on this limitation, we have done measurements on CBT sensors fabricated with different on-chip filtering structures in a dilution refrigerator with a base temperature of 10 mK. The CBT sensors were produced with a wafer scale tunnel junction process. We present how the different on-chip filtering schemes affect the limiting saturation temperatures and show that CBT sensors with proper on-chip filtering work at temperatures below 20 mK and are tolerant to noisy environment. © Published under licence by IOP Publishing Ltd.


Grant
Agency: European Commission | Branch: FP7 | Program: CP | Phase: SPA.2010.2.2-01 | Award Amount: 2.58M | Year: 2011

Recently, research in astrophysics has yielded amazing new insight in the origin, evolution and structure of the Universe, and fundamental processes governing this highly dynamical system. Most of this progress was achieved thanks to the availability of extremely sensitive detectors. Common features for such detectors are extremely low noise and very small background, and the main solutions for achieving this are based on extremely low operating temperature allowing measurement of signal in superconducting phase. Space-based applications using superconducting technology, however, are rare and considerable effort is being put in their development. In this critical field, European technology has recently fallen notably behind the state of the art defined by the USA. We will use Transition Edge Sensor (TES), Microwave Kinetic Inductance Detector (MKID), and Metallic Magnetic Calorimeter (MMC) detector arrays and develop readout systems using multiplexed Superconducting Quantum Interference Device (SQUID) amplifiers for focal plane sensor arrays in the X-rays, optical and far infrared wavelengths. The above detector concept has potential for use in a wide range of space missions, and it has also applications in other fields of research outside astronomy, where weak photon signals are measured with high accuracy. The main aim of this project is to improve the European technology readiness level (TRL) and brigde the gap to the global state-of-the-art and advance European independence in the above key technology. The partners of this collaborative project are the key developers of SQUID technology in Europe (VTT Finland, IPHT Germany), and represent the highest international level of scientific expertise in astrophysics research and instrument development (SRON Netherlands, University of Leicester United Kingdom, Max-Planck Institute for Radio Astronomy Germany, and University of Helsinki Finland). Also two SME partners are involved in minor supporting work packages.


PubMed | VTT Technical Research Center of Finland, Lancaster University, Aivon Oy and RAS Lebedev Physical Institute
Type: | Journal: Nature communications | Year: 2016

Cooling nanoelectronic structures to millikelvin temperatures presents extreme challenges in maintaining thermal contact between the electrons in the device and an external cold bath. It is typically found that when nanoscale devices are cooled to 10 mK the electrons are significantly overheated. Here we report the cooling of electrons in nanoelectronic Coulomb blockade thermometers below 4 mK. The low operating temperature is attributed to an optimized design that incorporates cooling fins with a high electron-phonon coupling and on-chip electronic filters, combined with low-noise electronic measurements. By immersing a Coulomb blockade thermometer in the (3)He/(4)He refrigerant of a dilution refrigerator, we measure a lowest electron temperature of 3.7 mK and a trend to a saturated electron temperature approaching 3 mK. This work demonstrates how nanoelectronic samples can be cooled further into the low-millikelvin range.

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