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Alonso, F. (2018). Models and Simulations of the Electric Field in Deep Brain Stimulation: Comparison of Lead Designs, Operating Modes and Tissue Conductivity. (Doctoral dissertation). Linköping: Linköping University Electronic Press
Open this publication in new window or tab >>Models and Simulations of the Electric Field in Deep Brain Stimulation: Comparison of Lead Designs, Operating Modes and Tissue Conductivity
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
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.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2018. p. 99
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1945
National Category
Other Medical Engineering
Identifiers
urn:nbn:se:liu:diva-150996 (URN)10.3384/diss.diva-150996 (DOI)9789176852613 (ISBN)
Public defence
2018-09-14, Grannitsalen, Campus US, Linköping, 09:00 (English)
Opponent
Supervisors
Available from: 2018-09-10 Created: 2018-09-10 Last updated: 2018-09-10Bibliographically approved
Alonso, F., Vogel, D., Wårdell, K. & Hemm-Ode, S. (2017). Comparison between intraoperative and chronic and deep brain stimulation. In: : . Paper presented at World Society for Stereotactic and Functional Neurosurgery, 17th Quadrennial meeting, Berlin June 26-29, 2017.
Open this publication in new window or tab >>Comparison between intraoperative and chronic and deep brain stimulation
2017 (English)Conference paper, Poster (with or without abstract) (Refereed)
Abstract [en]

INTRODUCTION

The success of the deep brain stimulation (DBS) therapy relies primarily in the localization of the implanted electrode, implying the need of utmost accuracy in the targeting process. Intraoperative microelectrode recording and stimulation tests are a common procedure before implanting the permanent DBS lead to determine the optimal position with a large therapeutic window where side effects are avoided and the best improvement of the symptoms is achieved. Differences in dimensions and operating modes exist between the exploration and the permanent DBS electrode which might lead to different stimulation fields, even when ideal placement is achieved. The aim of this investigation is to compare the electric field (EF) distribution around the intraoperative and the chronic electrode, assuming that both have exactly the same position.

METHODS

3D models of the intraoperative exploration electrode and the chronically implanted DBS lead 3389 (Medtronic Inc., USA) were developed using COMSOL 5.2 (COMSOL AB, Sweden). Patient-specific MR images were used to determine the conductive medium around the electrode. The exploration electrode and the first DBS contact were set to current and voltage respectively (0.2mA(V) - 3 mA(V) in 0.1 mA(V) steps). The intraoperative model included the grounded guide tube used to introduce the exploration electrode; for the chronic DBS model, the outer boundaries were grounded and the inactive contacts were set to floating potential considering a monopolar configuration. The localization of the exploration and the chronic electrode was set according to the planned trajectory. The EF was visualized and compared in terms of volume and extension using a fixed isocontour of 0.2 V/mm.

RESULTS

The EF distribution simulated for the exploration electrode showed the influence of the parallel trajectory and the grounded guide tube. For an amplitude of e.g. 2 mA/2 V, the EF extension of the intraoperative was 0.6 mm larger than the chronic electrode at the target level; the corresponding difference in volume was 76.1 mm3.

CONCLUSION

Differences in the EF shape between the exploration and the chronic DBS electrode have been observed using patient-specific models. The larger EF extension obtained for the exploration electrode responds to its higher impedance and the use of current controlled stimulation. The presence of EF around the guide tube and the influence of the parallel trajectory require further experimental and clinical evaluation.

National Category
Medical Engineering
Identifiers
urn:nbn:se:liu:diva-139880 (URN)
Conference
World Society for Stereotactic and Functional Neurosurgery, 17th Quadrennial meeting, Berlin June 26-29, 2017
Available from: 2017-08-21 Created: 2017-08-21 Last updated: 2017-08-21
Wårdell, K., Johansson, J. & Alonso, F. (2017). Deep brain stimulation: software for patient-specific electric field simulations. In: : . Paper presented at World Society for Stereotactic and Functional Neurosurgery, 17th Quadrennial meeting, Berlin June 26-29, 2017.
Open this publication in new window or tab >>Deep brain stimulation: software for patient-specific electric field simulations
2017 (English)Conference paper, Poster (with or without abstract) (Refereed)
Abstract [en]

Introduction

The electric field (EF) around the active deep brain stimulation (DBS) contact is of interest for optimizing the therapeutic effect. We have previously developed a method for simulation and visualization of the EF. The aim of the project is to improve the software for quick and user friendly simulations.  

Methods

The ELMA software for brain model creation has been improved by adding quick ROI selection and transformation to an electrical conductivity map based on tissue classification through multiple slices of the preoperative MRI. These data are used as input for Comsol Multiphysics simulations of the EF. Two points along the position of the lead, as seen in the postoperative images, are used for correct placement in the brain model. Multiple DBS lead models are pre-programmed. The active contact and amplitude are user-selected.

Results

After a simulation the result is visualized with a user defined isolevel or isosurface superimposed on the patients preoperative MRI. An example is shown in Fig. 1. The 3389 lead is places in zona inserta (Zi) and contact 1 activated with 2 and 4 V respectively. An isolevel of 0.2 V/mm is used corresponding to a ~ 3-4 µm axon diameter when using a pulse length of 60 µs. More examples will be presented at the meeting.

Conclusion

The software for patient-specific simulations of EF around DBS electrodes has been improved for quicker simulations and more DBS leads. As a next step user friendly Apps will be implemented.

National Category
Medical Engineering
Identifiers
urn:nbn:se:liu:diva-139879 (URN)
Conference
World Society for Stereotactic and Functional Neurosurgery, 17th Quadrennial meeting, Berlin June 26-29, 2017
Available from: 2017-08-21 Created: 2017-08-21 Last updated: 2017-08-21
Shah, A., Alonso, F., Lemarie, J.-J., Pison, D., Coste, J., Wårdell, K., . . . Hemm-Ode, S. (2017). Learning more about the optimal anatomical position for deep brain stimulation in essential tremor patients: 3D visualisation of intraoperative stimulation test results. In: : . Paper presented at World Society for Stereotactic and Functional Neurosurgery, 17th Quadrennial meeting, Berlin June 26-29, 2017.
Open this publication in new window or tab >>Learning more about the optimal anatomical position for deep brain stimulation in essential tremor patients: 3D visualisation of intraoperative stimulation test results
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2017 (English)Conference paper, Poster (with or without abstract) (Refereed)
Abstract [en]

INTRODUCTION

The outcome of deep brain stimulation (DBS) depends heavily on the position of the implanted lead. After a preoperative anatomical planning, most groups collect numerous intraoperative data such as therapeutic effects induced by stimulation tests. To choose the final implant position, physicians “mentally” visualise all available data. The aim of the present work was to develop a method visualising intraoperative stimulation test results, patient’s images, electric field (EF) simulations for the patient-specific stimulation conditions and the corresponding therapeutic effects quantitatively evaluated by accelerometry. The application to five essential tremor (ET) patients should give a first idea about the optimal target position. 

METHODS

In Clermont-Ferrand University Hospital the anatomic target structure and the neighbouring structures were manually outlined, a target and a trajectory defined and two parallel trajectories per hemisphere intraoperatively evaluated. Stimulation tests were performed at 7 to 8 positions per trajectory and several stimulation current amplitudes. The therapeutic effect was evaluated using a previously published method based on accelerometry. Finite element models and simulations were performed for up to three stimulation amplitudes per position and EF isosurfaces (0.2V/mm) were extracted. For the 3D visualization of the numerous overlapping isosurfaces, we generated “improvement maps” by assigning to each voxel within the isosurfaces the highest tremor improvement. Those maps were visualized together with anatomical images, delineated structures and trajectories (Paraview, Kitware Inc). The method was applied to 5 ET patients implanted in the ventro-intermediate nucleus of the thalamus (VIM). Results were analysed by the neurosurgeon regarding the optimal implant position.  

RESULTS

The clinical teams were able to identify the optimal implant position for all patients with more ease and in less time compared to the routine discussion using pen and paper. Additionally, for 7 of the 9 improvement maps, the highest improvement region was found to be in the posterior subthalamic area, inferior and posterior to the VIM.

CONCLUSION

Improvement maps assist the clinicians in determining the optimal implant location of the chronic DBS lead. Results support findings of other studies that the fibre tracts in the posterior subthalamic area like prelemniscal radiations may be responsible for alleviating tremor in ET patients.

National Category
Medical Engineering
Identifiers
urn:nbn:se:liu:diva-139878 (URN)
Conference
World Society for Stereotactic and Functional Neurosurgery, 17th Quadrennial meeting, Berlin June 26-29, 2017
Available from: 2017-08-21 Created: 2017-08-21 Last updated: 2017-08-21
Göransson, N., Johansson, J., Alonso, F., Wårdell, K. & Zsigmond, P. (2017). Postoperative lead movement after deep brain stimulation surgery and changes of stimulation area. In: : . Paper presented at World Society for Stereotactic and Functional Neurosurgery, 17th Quadrennial meeting, Berlin June 26-29, 2017. S. Karger
Open this publication in new window or tab >>Postoperative lead movement after deep brain stimulation surgery and changes of stimulation area
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2017 (English)Conference paper, Oral presentation with published abstract (Other academic)
Abstract [en]

Introduction

Lead movement after deep brain stimulation (DBS) may occur and influence the area of stimulation. The cause of the displacement is not fully understood. The aim of the study was to investigate differences in lead position between the day after surgery and approximately one month postoperatively and also simulate the electric field (EF) around the active contacts.

Methods

23 patients with movement disorders underwent DBS surgery (37 leads). CT at the two time points were co-fused respectively with the stereotactic images in Surgiplan. The coordinates (x, y, z) of the lead tips were compared between the two dates (paired t-test). 8 of these patients were selected for the EF simulation in Comsol Multiphysics.

Results

There was a significant discrepancy (mean ± s.d.) on the left lead: x (0.44 ± 0.72, p < 0.01), y (0.64 ± 0.54, p < 0.001), z (0.62 ± 0.71, p < 0.001).  On the right lead, corresponding values were: x (-0.11 ± 0.61, n.s.), y (0.71 ± 0.54, p < 0.001), z (0.49 ± 0.81, p < 0.05).  No correlation was found between bilateral (n =14) vs. unilateral DBS, gender (n = 17 male) and age < 60 years (n = 8).  The lead movement affected the EF spread (Fig. 1).

Conclusion

The left lead tip displayed a tendency to move lateral, anterior and inferior and the right a tendency to move anterior and inferior. Lead movement after DBS can be a factor to consider before starting the stimulation. The differences in the area of stimulation might affect clinical outcome.

Place, publisher, year, edition, pages
S. Karger, 2017
Series
Stereotactic and Functional Neurosurgery, ISSN 1011-6125, E-ISSN 1423-0372
National Category
Medical Engineering
Identifiers
urn:nbn:se:liu:diva-139886 (URN)10.1159/000478281 (DOI)
Conference
World Society for Stereotactic and Functional Neurosurgery, 17th Quadrennial meeting, Berlin June 26-29, 2017
Available from: 2017-08-21 Created: 2017-08-21 Last updated: 2017-09-04
Alonso, F., Wårdell, K. & Latorre, M. (2015). Comparison of Three Deep Brain Stimulation Lead Designs under Voltage and Current Modes. In: David A. Jaffray (Ed.), WORLD CONGRESS ON MEDICAL PHYSICS AND BIOMEDICAL ENGINEERING, 2015, VOLS 1 AND 2: . Paper presented at World congress on medical physics and biomedical engineering, Toronto, June 7-12, 2015 (pp. 1196-1199). Springer, 51
Open this publication in new window or tab >>Comparison of Three Deep Brain Stimulation Lead Designs under Voltage and Current Modes
2015 (English)In: WORLD CONGRESS ON MEDICAL PHYSICS AND BIOMEDICAL ENGINEERING, 2015, VOLS 1 AND 2 / [ed] David A. Jaffray, Springer, 2015, Vol. 51, p. 1196-1199Conference paper, Published paper (Refereed)
Abstract [en]

Since the introduction of deep brain stimulation (DBS) the technique has been dominated by Medtronic sys-tems. In recent years, new DBS systems have become available for patients, and some are in clinical trials. The present study aims to evaluate three DBS leads operated in either voltage or current mode. 3D finite element method (FEM) models were built in combination with a neuron model for this purpose. The axon diameter was set to D = 5 μm and simulations performed in both voltage (0.5-5 V) and current (0.5-5 mA) mode. The evaluation was achieved based on the distance from the lead for neural activation and the electric field (EF) extension at 0.1 V/mm. The results showed that the neural activation distance agrees well between the leads with an activation distance dif-ference less than 0.5 mm. The shape of the field at the 0.1 V/mm isopotential surface in 3D is mostly spherical in shape around the activated section of the steering lead.

Place, publisher, year, edition, pages
Springer, 2015
Series
IFMBE Proceedings, ISSN 1680-0737 ; 51
Keywords
deep brain stimulation (DBS), electrode design, finite element method (FEM), neuron model
National Category
Other Medical Engineering
Identifiers
urn:nbn:se:liu:diva-120637 (URN)10.1007/978-3-319-19387-8_290 (DOI)000381813000290 ()978-3-319-19386-1 (ISBN)978-3-319-19387-8 (ISBN)
Conference
World congress on medical physics and biomedical engineering, Toronto, June 7-12, 2015
Funder
Swedish Research Council, 621-2013-6078EU, FP7, Seventh Framework Programme, 305814
Available from: 2015-08-20 Created: 2015-08-20 Last updated: 2017-02-03Bibliographically approved
Alonso, F., Hemm-Ode, S. & Wårdell, K. (2015). Influence on Deep Brain Stimulation from Lead Design, Operating Mode and Tissue Impedance Changes – A Simulation Study. Brain Disorders and Therapy, 4(3), Article ID 1000169.
Open this publication in new window or tab >>Influence on Deep Brain Stimulation from Lead Design, Operating Mode and Tissue Impedance Changes – A Simulation Study
2015 (English)In: Brain Disorders and Therapy, ISSN 2168-975X, Vol. 4, no 3, article id 1000169Article in journal (Refereed) Published
Abstract [en]

Background: Deep brain stimulation (DBS) systems in current mode and new lead designs are recently available. To switch between DBS-systems remains complicated as clinicians may lose their reference for programming. Simulations can help increase the understanding.

Objective: To quantitatively investigate the electric field (EF) around two lead designs simulated to operate in voltage and current mode under two time points following implantation.

Methods: The finite element method was used to model Lead 3389 (Medtronic) and 6148 (St Jude) with homogenous surrounding grey matter and a peri-electrode space (PES) of 250 μm. The PES-impedance mimicked the acute (extracellular fluid) and chronic (fibrous tissue) time-point. Simulations at different amplitudes of voltage and current (n=236) were performed using two different contacts. Equivalent current amplitudes were extracted by matching the shape and maximum EF of the 0.2 V/mm isolevel.

Results: The maximum EF extension at 0.2 V/mm varied between 2-5 mm with a small difference between the leads. In voltage mode EF increased about 1 mm at acute compared to the chronic PES. Current mode presented the opposite relationship. Equivalent EFs for lead 3389 at 3 V were found for 7 mA (acute) and 2.2 mA (chronic).

Conclusions: Simulations showed a major impact on the electric field extension between postoperative time points. This may explain the clinical decisions to reprogram the amplitude weeks after implantation. Neither the EF extension nor intensity is considerably influenced by the lead design.

Place, publisher, year, edition, pages
Los Angeles, CA, USA: Omics Publishing Group, 2015
Keywords
deep brain stimulation (DBS), voltage and current stimulation, finite element method
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:liu:diva-120680 (URN)10.4172/2168-975X.1000169 (DOI)
Funder
Swedish Research Council, 621-2013-6078
Available from: 2015-08-21 Created: 2015-08-20 Last updated: 2018-09-10Bibliographically approved
Alonso, F., Wårdell, K. & Latorre, M. (2015). Neural Activation Compared to Electric Field Extension of Three DBS Lead Designs. In: : . Paper presented at 7TH INTERNATIONAL IEEE/EMBS CONFERENCE ON NEURAL ENGINEERING, Montpellier, April 22-24, 2015.
Open this publication in new window or tab >>Neural Activation Compared to Electric Field Extension of Three DBS Lead Designs
2015 (English)Conference paper, Poster (with or without abstract) (Refereed)
Abstract [en]

SINCE the introduction of deep brain stimulation (DBS) about 20 years ago, the stimulation technique has been dominated by Medtronic DBS-system setup. In recent years, new DBS systems have become available, of which some are in clinical trials or available to patients [1]. In the present study three different lead designs are investigated via computer simulation:

Medtronic 3389, St. Jude 6148 and Sapiens SureStim. The aim was to compare the neural activation distance and the electric field (EF) maximum spatial extension for each lead.

A 3D finite element method model was built using COMSOL Multiphysics 4.4a (COMSOL AB, Stockholm, Sweden) to simulate the electric potential around the DBS lead. Brain tissue was modelled as a homogeneous volume of grey matter (electric conductivity of 0.09 S/m). The electrode-tissue interface was modelled with a 250μm thick peri-electrode space mimicking the fibrous tissue which covers the lead at the chronic stimulation stage (σ = 0.06S/m, equivalent to white matter electric conductivity). The stimulation amplitude was set to 1V in monopolar configuration using C1 electrode or equivalent in all cases. Each simulated electric potential distribution was exported to MatLab (The MathWorks, USA) and used as input to a cable neuron simulation.

An axon cable model with 21 nodes based on the concept by Åström et al., [2] was set up in MatLab and combined with the exported field distributions. The model considered a 5 μm thick neuron, a pulse width of 60 μs and a drive potential ranging from 0.5 V to 5 V in 0.5 V steps.

The SureStim lead results showed a shorter neural activation distance and EF extension. The distance to the isolevel of 0.2 V/mm is close to the neural activation distance at each stimulation amplitude, and we conclude that the electric field is a suitable predictor to visualize the stimulated regions.

Keywords
DBS leads, neural activation, steering leads, finite element model
National Category
Other Medical Engineering
Identifiers
urn:nbn:se:liu:diva-120636 (URN)
Conference
7TH INTERNATIONAL IEEE/EMBS CONFERENCE ON NEURAL ENGINEERING, Montpellier, April 22-24, 2015
Funder
Swedish Research Council, 621-2013-6078EU, FP7, Seventh Framework Programme, 305814
Available from: 2015-08-20 Created: 2015-08-20 Last updated: 2017-02-03Bibliographically approved
Alonso, F. & Wårdell, K. (2014). Comparison of deep brain stimulation systems. In: Poster Presentations: . Paper presented at The MDS 18th International Congress of Parkinson's Disease and Movement Disorders, June 8-12, 2014, Stockholm, Sweden (pp. 1173-1173). , 29, Article ID Suppl 1.
Open this publication in new window or tab >>Comparison of deep brain stimulation systems
2014 (English)In: Poster Presentations, 2014, Vol. 29, p. 1173-1173, article id Suppl 1Conference paper, Poster (with or without abstract) (Other academic)
Abstract [en]

Objective: To quantitatively compare the electric field generated by voltage and current controlled deep brain stimulation systems.

Background: Traditionally deep brain stimulation (DBS) systems have used voltage control however more recently, current controlled systems have been approved to treat Parkinson's disease and related movement disorders. In the endeavor of understanding the behavior of DBS systems a common approach is the use of computer models suitable to simulate the electric field, current density and other related electric parameters.

Methods: 2D finite element models based on commercially available DBS systems have been built for each system: I. Model 3389, Medtronic Inc., USA for voltage control; and II. Model 6142, St Jude Medical Inc. USA for current control. The brain tissue has been simplified to homogeneous and isotropic medium. The electric settings correspond to a monopolar configuration, using one of the four contacts available as the active electrode and the outer boundary of the tissue as the reference. Three simulations were performed to mimic different stages of the leads implantation: a) an original stage where the brain tissue is considered as pure gray matter, b) an acute stage that simulates the leakage of cerebral spinal fluid immediately after the electrodes' insertion; and c) a chronic stage mimicking fibrous tissue created around the electrodes some weeks after implantation. Both systems were submitted to the same conditions using as active electrode the third contact from the tip of the lead. The comparison is based on the maximal distance reached by the isopotential of 0.2 V/mm.

Results: The simulations showed that voltage controlled stimulation systems are more susceptible to changes in the electrical conductivity of the medium i.e. change over time of the tissue around the electrode. This agrees with the adjustment of the stimulation amplitude often necessary a few weeks postoperatively. Current controlled stimulation in turn, presented a linear behavior of the distance reached at different stimulation amplitudes at all stages.

Conclusions: Current controlled stimulation might be a good option due to its linear behavior over time, nevertheless more studies including a more realistic brain model, different designs of DBS electrodes and different electric parameter, are needed to encourage the use of this type of systems.

National Category
Other Medical Engineering
Identifiers
urn:nbn:se:liu:diva-107599 (URN)10.1002/mds.25914 (DOI)
Conference
The MDS 18th International Congress of Parkinson's Disease and Movement Disorders, June 8-12, 2014, Stockholm, Sweden
Available from: 2014-06-17 Created: 2014-06-17 Last updated: 2017-02-14Bibliographically approved
Alonso, F. (2014). Modeling and simulation of DBS – comparison between leads and stimulation modes. In: : . Paper presented at 1st IMPACT Workshop and 7th NeuroTech Workshop, May 15-16, 2014, Linköping, Sweden.
Open this publication in new window or tab >>Modeling and simulation of DBS – comparison between leads and stimulation modes
2014 (English)Conference paper, Oral presentation only (Other academic)
National Category
Other Medical Engineering
Identifiers
urn:nbn:se:liu:diva-107606 (URN)
Conference
1st IMPACT Workshop and 7th NeuroTech Workshop, May 15-16, 2014, Linköping, Sweden
Available from: 2014-06-17 Created: 2014-06-17 Last updated: 2017-02-03Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-6896-1452

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