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Investigation into Deep Brain Stimulation Lead Designs: A Patient-Specific Simulation Study
Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering. (MINT)ORCID iD: 0000-0002-6896-1452
Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering. (MINT)
Linköping University, Department of Biomedical Engineering. Linköping University, Faculty of Science & Engineering. Region Östergötland, Anaesthetics, Operations and Specialty Surgery Center, Department of Neurosurgery. (MINT)
Region Östergötland, Anaesthetics, Operations and Specialty Surgery Center, Department of Neurosurgery. Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences.
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Number of Authors: 5
2016 (English)In: Brain Sciences, ISSN 2076-3425, E-ISSN 2076-3425, Vol. 6, no 3, 1-16 p.Article in journal (Refereed) Published
Abstract [en]

New deep brain stimulation (DBS) electrode designs offer operation in voltage and current mode and capability to steer the electric field (EF). The aim of the study was to compare the EF distributions of four DBS leads at equivalent amplitudes (3 V and 3.4 mA). Finite element method (FEM) simulations (n = 38) around cylindrical contacts (leads 3389, 6148) or equivalent contact configurations (leads 6180, SureStim1) were performed using homogeneous and patient-specific (heterogeneous) brain tissue models. Steering effects of 6180 and SureStim1 were compared with symmetric stimulation fields. To make relative comparisons between simulations, an EF isolevel of 0.2 V/mm was chosen based on neuron model simulations (n = 832) applied before EF visualization and comparisons. The simulations show that the EF distribution is largely influenced by the heterogeneity of the tissue, and the operating mode. Equivalent contact configurations result in similar EF distributions. In steering configurations, larger EF volumes were achieved in current mode using equivalent amplitudes. The methodology was demonstrated in a patient-specific simulation around the zona incerta and a “virtual” ventral intermediate nucleus target. In conclusion, lead design differences are enhanced when using patient-specific tissue models and current stimulation mode.

Place, publisher, year, edition, pages
MDPI , 2016. Vol. 6, no 3, 1-16 p.
Keyword [en]
deep brain stimulation (DBS), steering, patient-specific, electric field, finite element method, neuron model, brain model, zona incerta (ZI), electrode design
National Category
Medical Engineering
Identifiers
URN: urn:nbn:se:liu:diva-131863DOI: 10.3390/brainsci6030039PubMedID: 27618109OAI: oai:DiVA.org:liu-131863DiVA: diva2:1034148
Available from: 2016-10-11 Created: 2016-10-11 Last updated: 2017-11-29Bibliographically approved
In thesis
1. The Physical Axon: Modeling, Simulation and Electrode Evaluation
Open this publication in new window or tab >>The Physical Axon: Modeling, Simulation and Electrode Evaluation
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Electrodes are used in medicine for detection of biological signals and for stimulating tissue, e.g. in deep brain stimulation (DBS). For both applications, an understanding of the functioning of the electrode, and its interface and interaction with the target tissue involved is necessary. To date, there is no standardized method for medical electrode evaluation that allows transferability of acquired data. In this thesis, a physical axon (Paxon) potential generator was developed as a device to facilitate standardized comparisons of different electrodes. The Paxon generates repeatable, tuneable and physiological-like action potentials from a peripheral nerve. It consists of a testbed comprising 40 software controlled 20 μm gold wires embedded in resin, each wire mimicking a node of Ranvier. ECG surface Ag-AgCl electrodes were systematically tested with the Paxon. The results showed small variations in orientation (rotation) and position (relative to axon position) which directly impact the acquired signal. Other electrode types including DBS electrodes can also be evaluated with the Paxon.

A theoretical comparison of a single cable neuronal model with an alternative established double cable neuron model was completed. The output with regards to DBS was implemented to comparing the models. These models were configured to investigate electrode stimulation activity, and in turn to assess the activation distance by DBS for changes in axon diameter (1.5-10 μm), pulse shape (rectangular biphasic and rectangular, triangular and sinus monophasic) and drive strength (1-5 V or mA). As both models present similar activation distances, sensitivity to input shape and computational time, the neuron model selection for DBS could be based on model complexity and axon diameter flexibility. An application of the in-house neuron model for multiple DBS lead designs, in a patient-specific simulation study, was completed. Assessments based on the electric field along multiple sample planes of axons support previous findings that a fixed electric field isolevel is sufficient for assessments of tissue activation distances for a predefined axon diameter and pulse width in DBS.

Abstract [sv]

Elektroder används inom sjukvården, både för att mäta biologiska signaler, t.ex. hjärtats aktivitet med EKG, eller för att stimulera vävnad, t.ex. vid djup hjärnstimulering (DBS). För båda användningsområdena är det viktigt med en grundläggande förståelse av elektrodens interaktion med vävnaden. Det finns ingen standardiserad metod för att utvärdera medicinsk elektroders dataöverföringsfunktion. I den här avhandlingen presenteras en metod för att underlätta elektrodtestning. En hårdvarumodell av ett axon (Paxon) har utvecklats. Paxon kan programmeras för att efterlikna repeterbara aktionspotentialer från en perifer nerv. Längs axonet finns 40 noder, vilka var och en består av en tunn (20 μm) guldtråd inbäddad i harts och därefter kopplad till elektronik. Denna testbädd har använts för att undersöka EKG elektroders egenskaper. EKG elektroderna visade på variationer i orientering och position i relation till Paxon. Detta har en direkt inverkan på den registrerade signalen. Även andra elektrotyper kan testas i Paxon, t.ex. DBS elektroder.

En teoretisk jämförelse mellan två neuronmodeller med olika komplexitet, anpassade för användning vid DBS studier, har utförts. Modellerna konfigurerades för att studera inverkan på aktiveringsavstånd från olika axondiametrar, stimulationspuls och stimulationsstyrka. Då båda modellerna visade likvärdiga aktiveringsavstånd och beräkningstid så förordas den enklare neuronmodellen för DBS simuleringar. En enklare modell kan lättare introduceras i klinisk verksamhet. Simuleringarna stöder tidigare resultat som visat att det elektriska fältet är en bra parameter för presentation av resultat vid simulering av DBS. Metoden exemplifieras vid simulering av aktiveringsavstånd och elektriska fältets utbredning för olika typer av DBS elektroder i en patient-specifik studie.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2017. 75 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1847
National Category
Medical Laboratory and Measurements Technologies Other Medical Engineering Biomedical Laboratory Science/Technology Computer Systems
Identifiers
urn:nbn:se:liu:diva-138587 (URN)10.3384/diss.diva-138587 (DOI)9789176855294 (ISBN)
Public defence
2017-08-25, Campus US, Linköpings universitet, Linköping, 09:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council, 621-2013-6078Swedish Research Council, 2016-03564Linköpings universitetSwedish Foundation for Strategic Research , BD15-0032
Available from: 2017-06-19 Created: 2017-06-19 Last updated: 2017-08-21Bibliographically approved

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