Deep brain stimulation (DBS) is a clinically effective treatment for movement disorders, including Parkinson’s disease and essential tremor. The number of patients treated with DBS is rapidly increasing (> 150,000 worldwide). The knowledge of the precise position of the implanted electrode in the brain in combination with the adjustable stimulation parameters and the resulting stimulation area in the human brain are essential for the best treatment of DBS patients. The aim of this project is to detect the position of the DBS electrode in patients and additionally to determine its rotation based on the orientation marker on the electrode. This will allow for calculating the stimulated area in the brain. The magnetoelectric (ME) sensors being developed within the framework of the collaborative research center (CRC) 1261 will be used for this purpose. The position of the electrode as well as the orientation of the rotation (which is surgically uncontrollable) can be detected with this tool, thereby avoiding radiation for the patients currently exposed to MRI or CT (position) or fluoroscopy (orientation). Research in the first funding period had laid the foundations for this.

In the first work package, the (newly and continuously) developed CRC sensors will be evaluated on the basis of important characteristics of such sensors for this application. The selected sensors will then be used to perform magnetic field measurements for reconstruction of the DBS electrode that has been successfully developed for a simplified phantom in the first funding period under B5. This needs to be extended to the individual brain imaging (CT/MRI) of patients with implanted electrodes in the second work package of this project. The detection of the directional electrode orientation in the phantom will be an additional part of this work package. The electrophysiological localization and orientation results will then be integrated into the individual neuroimaging data (preoperative MRI and postoperative CT/MRI) in the third work package. The localization of the electrode in the brain can be performed with several software programs, e.g. by using the open-source toolbox Lead-DBS that is developed in a DFG-Emmy-Noether group (Dr. Andreas Horn, Charité Berlin) for research purposes. In the next step, also in work package two, the stimulated electrical field with respect to the anatomical structures in the brain will be calculated for the individual stimulation parameters and implemented in such a system.

We plan to develop a software package that can be wrapped into image-based software to display the magnetically measured and reconstructed electrical fields within the individual MRI of the patient. Comparing this in silico imaging with the best point for stimulation for specific symptoms will be a helpful tool for better programming of the DBS devices of such patients. We established a cooperation with the company Boston Scientific (producer of DBS equipment and surgical planning and programming software), which had shown interest and is ready to contribute further to this transfer project. The collaboration will ensure in this transfer project that the medical and industrial requirements are considered and that the evaluation will be performed with state-of-the-art stimulators and industrial routines. The main motivation of the company is the possibility to measure the position and rotation of the segmented electrode non-radiatively. The close collaboration will serve to design a system for the calculation of the tissue activated by deep brain stimulation and to test its accuracy in various clinical studies where the side effects and effects can be clinically measured to validate this model.

 

Project-related Publications

M. Yalaz, G. Deuschl, M. Butz, A. Schnitzler, A-K. Helmers, M. Höft, Investigation of Magnetoelectric Sensor Requirements for Deep Brain Stimulation Electrode Localization and Rotational Orientation Detection. Sensors. (2021). doi:10.3390/s21072527

M. Yalaz, S. Noor, C. McIntyre, M. Butz, A. Schnitzler, G. Deuschl, M. Höft, DBS electrode localization and rotational orientation detection using SQUID-based magnetoencephalography, Journal of Neural Engineering 2021; doi:10.1088/1741-2552/abe099

M. Yalaz, A. Teplyuk, G. Deuschl, M. Höft, Dipole Fit Localization of the Deep Brain Stimulation Electrode using 3D Magnetic Field Measurements, IEEE Sensors Journal, (2020). doi:10.1109/JSEN.2020.2988067

M. Yalaz, A. Teplyuk, M. Muthuraman, G. Deuschl, M. Höft, The Magnetic Properties of Electrical Pulses delivered by Deep Brain Stimulation Systems, IEEE Trans on Instrumentation and Measurement, (2019). doi:10.1109/TIM.2019.2945744

Magnetoelectric Sensors for Movement Detection and Analysis

Neurological diseases associated with pathological movements (NDPMs) such as Parkinson’s disease, stroke, and multiple sclerosis affect millions of people worldwide. The evaluation of these diseases is typically performed by medical professionals in a clinic or doctor’s practice using qualitative or, at best, semi-quantitative approaches.

Two quantitative movement assessment techniques have already found their way into clinical research and, at least with pilot systems, into clinical management: complex stationary lab assessments and inertial measurement units (IMUs). Complex stationary lab assessments are extremely accurate and allow detailed, timesynchronized, comprehensive analyses of movement patterns. Disadvantages are high cost and relatively inflexible and time-consuming assessments. In contrast, IMUs, most often based on acceleration assessment with accelerometry and angular measurement with gyroscopes, have the advantage of flexible application. Disadvantages are data synchronization difficulties and time-related signal drift. Moreover, these techniques do not provide a comprehensive picture of body movements, neither in a global coordinate system nor in relation to a specific part of the body, e.g. the lower back.

We propose here an entirely novel movement detection strategy based on magnetoelectric (ME) sensors (combined with IMUs) that has the potential to combine almost all advantages of the movement detection techniques currently in use (e.g. flexible use, relatively cheap, unobtrusive, exact, and objective), while overcoming most of the respective disadvantages (e.g. not bound to a specific environment). This system will substantially add to our general understanding of physiological and pathological human movement under supervised and unsupervised conditions. It will eventually add to the quality of treatment evaluation of NDPMs (significant reduction of drift, improved localization performance).

 

Walter Maetzler
Prof. Dr. med.
Gerhard Schmidt
Prof. Dr.-Ing.
Lead of projects B2, B9, B10, and Z2
Hansen Clint
Dr.
Postdoc
Johannes Hoffmann
M.Sc.
Doctoral researcher

 

Role within the Collaborative Research Centre

Z1: This project is closely interlinked with the ME-sensor projects, especially those that operate in resonance. Such sensors are mainly produced in Z1.
B1, Z2: B9 will benefit from B1 and Z2 adapting system frontends and small sensor arrays to the re-quirements of B9. In turn, we will communicate test results back to B1/Z2 to facilitate the de-velopment of suitable measurement systems after transfer of mature sub-systems to Z2.
B2, B10: The project will use the same real-time framework as projects B2 and B10. Thus, all extensions made in either one of the projects will benefit the other and immediately speed up development.
B10, T1: All study participant management and data acquisition procedures will be shared with project B10 and T1.
T1: T1 and B9 will recruit PD patients jointly and evaluate at least 2 patients together.

 

Project-related Publications

J. Hoffmann, E. Elzenheimer, C. Bald, C. Hansen, W. Maetzler, G. Schmidt, Magnetoelektrische Sensoren zur Bewegungsdetektion und -analyse, Biosignale Workshop, 2020, Kiel, Germany

Magnetoelectric Sensor Systems for Cardiologic Applications

Current standard electrocardiography is a useful and easily applicable method that has been in clinical use for more than hundred years. However, it is hampered by low spatial resolution. Thus, precise electro-anatomical mapping of arrhythmias still has to be conducted by invasive catheterization. The main long-term objective of this project is to answer the question whether invasive mapping of arrhythmic substrates (current standard) can be replaced by a non-invasive alternative, namely analyses using signals obtained from ME sensors combined with electric measurements.

We will thus investigate if a multi-channel combined ECG/MCG (electrocardiogram/magnetocardiogram) approach allows for reliable non-invasive localization of the origin of cardiac arrhythmias. This is becoming even more important, as recently stereotactic body radiation therapy was successfully applied for ablation of ventricular tachycardia, promising a completely non-invasive way to cure arrhythmias in the future.

To perform the required measurements with a multitude of magnetic (both ME sensors originating from this CRC and already established systems) as well as electric sensors, individual real-time signalto-noise ratio estimations of all involved sensors will be investigated that permit optimal sensor placement, sensor signal combination, and parameter extraction. An appropriate automatic signal quality analysis should guarantee a minimum recording time for patients. To answer these research questions, forward modelling and a solution of the inverse problem is necessary. Here the results of the former CRC project B3 will be used and further extended. To evaluate the accuracy and clinical utility of this approach, we plan to compare it with results from electrophysiological studies (current standard) in 3 different groups of patients:

  • premature ventricular contractions,
  • idiopathic ventricular tachycardia,
  • ischemic ventricular tachycardia.

For each patient, magnetic resonance imaging (MRI) and computed tomography (CT) for anatomy and electric and magnetic measurements will be performed.

 

Gerhard Schmidt
Prof. Dr.-Ing.
Lead of projects B2, B9, B10, and Z2
Norbert Frey
Prof. Dr. med.
Lead of project B10
Erik Engelhardt
M.Sc.
Doctoral researcher

 

Role within the Collaborative Research Centre

Z1: This project is closely interlinked with the ME sensor projects, especially those that allow for low frequency (5 to 30 Hz) measurements
A8: The sensor models that are investigated in A8, will be incorporated in the forward modelling. A first sensor model version available in 2021 will be replaced with extended versions in 2023.
B1, Z2: B10 will benefit from B1 adapting system front-ends and small sensor arrays to the requirements of B10. In turn, we will communicate test results back to B1 to facilitate the development of suit- able measurement systems after transfer of mature sub-systems to Z2.
B2, B9: The project will use the same real-time framework as B2 and B9. Thus, all extensions made in either one of the projects will benefit the other and immediately speed up development.
B9,T1: All study participant management and data acquisition procedures will be shared with B9 and T1.

 

Project-related Publications

J. Reermann, E. Elzenheimer, G. Schmidt, Real-time Biomagnetic Signal Processing for Uncooled Magnetometers in Cardiology. IEEE Sensors Journal, Volume 15, Number 10, Pages 4237-4249 (2019). DOI: 10.1109/JSEN.2019.2893236

As part of the research in A3 in the previous funding period, it was shown that surface acoustic wave (SAW) sensors using the ΔE-effect can be used for very sensitive, broadband magnetic field sensing. These sensors are based on a patented approach using shear horizontal acoustic surface waves that are guided by a fused silica layer (Love waves) with an amorphous magnetostrictive FeCoSiB thin film on top. The velocity of these waves follows the magnetoelastic-induced changes of the shear modulus according to the magnetic field present. The delay line operation of the SAW sensor translates these changes into a phase shift. With an extremely low magnetic noise level of approximately 70 pT/Hz1/2 at 10 Hz, a bandwidth of 50 kHz and a dynamic range of 120 dB, this magnetic field sensor system shows outstanding characteristics. In addition to piezoelectric bulk crystals, polycrystalline thin-film AlScN on a silicon substrate will be investigated as a possible alternative, since its electro-acoustic coupling coefficient is clearly superior, especially in the high frequency domain. A main objective is to derive a comprehensive model for the sensitivity and the noise of magnetic field SAW sensors. This work will be performed in close collaboration with A1 on the magnetostrictive film, with A8 on modelling of design parameters as well as of the acoustic wave propagation, with A10 on magnetic noise modelling and characterization, and with B1 on the overall noise models. The major questions will include the concept and realization of the magnetostrictive component and investigations on the frequency, which is of course not independent from the magnetostrictive material of choice.

Besides this general objective, the following sub-objectives will guide the corresponding work packages, while the major results will be included in the signal-to-noise model: (1) For single crystalline SAW sensors, the choice of the piezoelectric single crystals and the material and layout of the guiding layer will be investigated as important parameters for the sensors´ performance; (2) for thin film SAW sensors, the acoustic mode and the layout of the sensor will be investigated and compared to our reference single crystalline SAW sensors; and (3) for phononic crystals, acoustic band gaps with defect-induced transmission windows as well as the micromagnetic fine-structure of the individual magnetic lattice elements will be investigated.

Contact

sfb1261@tf.uni-kiel.de

Chairman:

Prof. Dr. Eckhard Quandt

Kiel University
Institute for Materials Science

 

Internal server

 

CAU

Christian-Albrechts-Universität zu Kiel (CAU)

Christ.-Albrechts-Platz 4
D-24118 Kiel

UKSH

University Hospital Schleswig-Holstein, Campus Kiel (UKSH)

Arnold-Heller-Straße 3
D-24105 Kiel

ISIT

Fraunhofer Institute for Silicon Technology, Itzehoe (ISIT)

Fraunhoferstrasse 1
D-25524 Itzehoe  

IPN

IPN - Leibniz-Institut für die Pädagogik der Naturwissenschaften und Mathematik 

Olshausenstraße 62 
D-24118 Kiel

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