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Investigation into Deep Brain Stimulation Lead Designs: A Patient-Specific Simulation Study
Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska fakulteten. (MINT)ORCID-id: 0000-0002-6896-1452
Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska fakulteten. (MINT)
Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten. Region Östergötland, Sinnescentrum, Neurokirurgiska kliniken US. (MINT)
Region Östergötland, Sinnescentrum, Neurokirurgiska kliniken US. Linköpings universitet, Institutionen för klinisk och experimentell medicin, Avdelningen för neuro- och inflammationsvetenskap. Linköpings universitet, Medicinska fakulteten.
Visa övriga samt affilieringar
Antal upphovsmän: 52016 (Engelska)Ingår i: Brain Sciences, ISSN 2076-3425, E-ISSN 2076-3425, Vol. 6, nr 3, s. 1-16Artikel i tidskrift (Refereegranskat) 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.

Ort, förlag, år, upplaga, sidor
MDPI , 2016. Vol. 6, nr 3, s. 1-16
Nyckelord [en]
deep brain stimulation (DBS), steering, patient-specific, electric field, finite element method, neuron model, brain model, zona incerta (ZI), electrode design
Nationell ämneskategori
Medicinteknik
Identifikatorer
URN: urn:nbn:se:liu:diva-131863DOI: 10.3390/brainsci6030039PubMedID: 27618109OAI: oai:DiVA.org:liu-131863DiVA, id: diva2:1034148
Tillgänglig från: 2016-10-11 Skapad: 2016-10-11 Senast uppdaterad: 2019-11-11Bibliografiskt granskad
Ingår i avhandling
1. The Physical Axon: Modeling, Simulation and Electrode Evaluation
Öppna denna publikation i ny flik eller fönster >>The Physical Axon: Modeling, Simulation and Electrode Evaluation
2017 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
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.

Ort, förlag, år, upplaga, sidor
Linköping: Linköping University Electronic Press, 2017. s. 75
Serie
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1847
Nationell ämneskategori
Medicinsk laboratorie- och mätteknik Annan medicinteknik Biomedicinsk laboratorievetenskap/teknologi Datorsystem
Identifikatorer
urn:nbn:se:liu:diva-138587 (URN)10.3384/diss.diva-138587 (DOI)9789176855294 (ISBN)
Disputation
2017-08-25, Campus US, Linköpings universitet, Linköping, 09:00 (Engelska)
Opponent
Handledare
Forskningsfinansiär
Vetenskapsrådet, 621-2013-6078Vetenskapsrådet, 2016-03564Linköpings universitetStiftelsen för strategisk forskning (SSF), BD15-0032
Tillgänglig från: 2017-06-19 Skapad: 2017-06-19 Senast uppdaterad: 2019-10-11Bibliografiskt granskad
2. Models and Simulations of the Electric Field in Deep Brain Stimulation: Comparison of Lead Designs, Operating Modes and Tissue Conductivity
Öppna denna publikation i ny flik eller fönster >>Models and Simulations of the Electric Field in Deep Brain Stimulation: Comparison of Lead Designs, Operating Modes and Tissue Conductivity
2018 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Deep brain stimulation (DBS) is an established surgical therapy for movement disorders such as Parkinson’s disease (PD) and essential tremor (ET). A thin electrode is implanted in a predefined area of the brain with the use of stereotactic neurosurgery. In the last few years new DBS electrodes and systems have been developed with possibilities for using more parameters for control of the stimulation volume.

In this thesis, simulations using the finite element method (FEM) have been developed and used for investigation of the electric field (EF) extension around different types of DBS lead designs (symmetric, steering) and stimulation modes (voltage, current). The electrode surrounding was represented either with a homogeneous model or a patient-specific model based on individual preoperative magnetic resonance imaging (MRI). The EF was visualized and compared for different lead designs and operating modes.

In Paper I, the EF was quantitatively investigated around two lead designs (3389 and 6148) simulated to operate in voltage and current mode under acute and chronic time points following implantation.Simulations showed a major impact on the EF extension between postoperative time points which may explain the clinical decisions to change the stimulation amplitude weeks after implantation. In Paper II, the simulations were expanded to include two leads having steering function (6180, Surestim1) and patient-specific FEM simulations in the zona incerta. It was found that both the heterogeneity of the tissue and the operating mode, influence the EF distribution and that equivalent contact configurations of the leads result in similar EF. The steering mode presented larger volumes in current mode when using equivalent amplitudes. Simulations comparing DBS and intraoperative stimulation test using a microelectrode recording (MER) system (Paper III), showed that several parallel MER leads and the presence of the non-active DBS contacts influence the EF distribution and that the DBS EF volume can cover, but also extend to, other anatomical areas.

Paper IV introduces a method for an objective exploitation of intraoperative stimulation test data in order to identify the optimal implant position in the thalamus of the chronic DBS lead. Patient-specific EF simulations were related to the anatomy with the help of brain atlases and the clinical effects which were quantified by accelerometers. The first results indicate that the good clinical effect in ET is due to several structures around the ventral intermediate nucleus of the thalamus.

Ort, förlag, år, upplaga, sidor
Linköping: Linköping University Electronic Press, 2018. s. 99
Serie
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1945
Nationell ämneskategori
Annan medicinteknik
Identifikatorer
urn:nbn:se:liu:diva-150996 (URN)10.3384/diss.diva-150996 (DOI)9789176852613 (ISBN)
Disputation
2018-09-14, Grannitsalen, Campus US, Linköping, 09:00 (Engelska)
Opponent
Handledare
Tillgänglig från: 2018-09-10 Skapad: 2018-09-10 Senast uppdaterad: 2019-09-26Bibliografiskt granskad

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