Optically-pumped magnetometers (OPMs) have been emerging as highly sensitive low-frequency magnetic field sensors. This satellite meeting presents the progress in the development of these sensors and the status of their application to biomedical measurements such as magnetoencephalography (MEG), magnetocardiography (MCG), and magnetorelaxometry (MRX). The possible combination of OPM-based MEG with other modalities will also be discussed. The meeting will include different sensor designs, the status of on-scalp multichannel imaging systems based on individual OPM sensor heads, and the results of validation experiments. Furthermore, this symposium will include modeling results on the advantages of on-scalp MEG and suggested requirements for future models, sensors, and systems. A special emphasis will be placed on also presenting the latest status of several commercial OPM efforts.

Speakers:

Samu Taulu (Univ. of Washington, USA)
“Basic principles of MEG and the effect of measurement geometry on multichannel signal representation, preprocessing, and data analysis”

Joonas Iivanainen (Aalto Univ., Finland)
“Performance of near-scalp arrays in MEG: Simulation studies”

Matt Brookes (Univ. of Nottingham, UK)
“OPM MEG: Simulations and initial results”

Peter Schwindt (Sandia Nat’l Lab., USA)
“Principles of optically pumped magnetometers and a survey of biomagnetic applications”

Peter Schwindt (Sandia Nat’l Lab., USA)
“A multichannel magnetoencephalography system using optically-pumped magnetometers”

Yoshio Okada (Boston Children’s Hospital, USA)
“Integrated multichannel cryoTMS and AM-MEG system”

Kasper Jensen (Univ. of Copenhagen, Denmark)
“Non-invasive detection of animal nerve impulses with an atomic magnetometer operating near quantum limited sensitivity”

Tetsuo Kobayashi (Kyoto Univ., Japan)
“Development of compact OPMs towards innovative biomagnetic imaging systems”

Svenja Knappe (Nat’l Inst. of Standards and Technology, USA)
“Biomagnetic imaging with microfabricated optically-pumped magnetometer arrays”

Vishal Shah (QuSpin Inc., USA)
“Commercial OPMs for Biomagnetism: Results from Pilot Production”

Tom Kornack (Twinleaf LLC, USA)
“Twinleaf optical magnetometers”

Rahul Mhaskar (Geometrics Inc., USA)
“Multi-channel MCG in an unshielded environment using scalar OPMs”

Optimal nanostructuring of the active strip (AS) of a magnetic field concentrator (MFC) based on superconducting films makes it possible to additionally enhance the concentration factor1. We calculated concentration factors F and F0 for the nanostructured AS with nanosized cuts and for the AS without nanostructuring. In the calculation, we took into account inductances of MFC receiving rings.
The positions of cuts in the AS, magnetosensitive element (MSE) width w0, and London penetration depth  were varied. The MSE was placed between two MFC rings, which lied in one plane and did not intersect. In the calculations, we assumed that the cut width wp coincides with the gap wa between the near MFC and MSE edges and the AS width ws and AS branch width are multiple to wa.
The results of the calculation are given in Table 1. The parameters used were as follows: w0 = 0.2, 1, and 5 m; = 50 and 250 nm; Jc = 1010 A/m2; the AS semithickness in the MSE h = 10 nm; ws = 30 m; ring radius rL = 1 mm; ring thickness wL = 0.8 mm; and wa = wp = 20 nm. It can be seen that with a decrease in w0 the F0 value increases and the F value decreases, but the total concentration factor F* grows. The MFC made of low-temperature superconducting materials, e.g., niobium with = 50 nm, has the higher efficiency than the MFC made of high-temperature superconducting materials, e.g., Y-123 and Bi-2223 with ≥ 250 nm.
The investigated MFC with nanosized cuts will make it possible to enhance the efficiency of combined magnetic field sensors, SQUIDS, and other sensors with a resolution of ≤ 1 pT.

Theoretical and Practical aspects of tCS.
- General overview of tCS (Transcranial Current Stimulation) for both researchers and clinicians.
- Main applications.
- Review of relevant clinical trials.
- Hands on sessions.

Speakers:

Rafal Nowak (Neuroelectrics Barcelona, Spain)
“Introduction of tCS “

Alejandro Riera (Neuroelectrics Barcelona, Spain)
“Clinical Applications of tCS”

Rafal Nowak (Neuroelectrics Barcelona, Spain)
“Starstim/Enobio hands on“

Alejandro Riera (Neuroelectrics Barcelona, Spain)
“BCI and ERP applications”

Toralf Neuling (Univ. of Salzburg, Austria)
“Oscillatory phase shapes perception. tACS stimulation with EEG, MEG and fMRI”

Yun Kim (Samsung Medical Center, Korea)
“tCS appllication on Stroke neurorehabilitation”

Surjo Soekadar (Univ. of Tuebingen, Germany)
“Real-time reconstruction of brain oscillatory activity during tACS and tDCS”

Present whole-head MEG systems rely on liquid helium to cool the helmet SQUID array, and the periodic refill of the liquid helium is the main running expense of the MEG system. In addition, helium resource is finite and is getting more difficult to get. If the low-noise SQUID array made of low-temperature superconductor can be cooled continuously without refill of liquid helium, it will greatly reduce the running cost and eliminate the effort to refill the liquid helium periodically. In the reliquefier MEG concept, the evaporating helium gas is reliquefied by the cryocooler and transferred to the MEG dewar continuously, resulting in zero boil off of liquid helium. In the meeting, the following topics will be covered: introduction to cryogenics and reliquefier concept based on 4 K cryocooler, reduction of vibration and magnetic noises caused by the cryocooler, and successful examples of continuous MEG operation using the reliquefier concept.

Speakers:

Chao Wang (Cryomech, Inc., USA)
“Liquid helium solutions with 4 K pulse tube cryocoolers”

Yong-Ho Lee (KRISS, Korea)
“Analysis of magnetic noise and vibration in reliquefier-based MEG system”

Limin Sun (Boston Children's Hospital/Harvard Medical School, USA)
“Closed-cycle helium recycler for continuous uninterrupted operation of low-Tc SQUID MEG systems”

Yoshiaki Adachi (Kanazawa Inst. of Tech., Japan)
“SQUID Biomagnetic Measurement Systems with Closed-cycle LHe Recondensing”

Tsunehiro Takeda (Frontier Technology Inst. Co., Ltd, Japan)
“HCS (Helium Circulation System) present and its future development”

Petteri Laine (Elekta Neuromag, Oy, Finaland)
“Elekta Neuromag zero helium boil-off technology”