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Publications (10 of 14) Show all publications
Alonso, F. (2019). Deep brain stimulation: Patient-specific modelling, simulation and visualization of  DBS electric field. In: : . Paper presented at Institute of Neurobiology UNAM Mexico.
Open this publication in new window or tab >>Deep brain stimulation: Patient-specific modelling, simulation and visualization of  DBS electric field
2019 (Spanish)Conference paper, Oral presentation only (Other (popular science, discussion, etc.))
National Category
Other Medical Engineering
Identifiers
urn:nbn:se:liu:diva-160750 (URN)
Conference
Institute of Neurobiology UNAM Mexico
Available from: 2019-10-07 Created: 2019-10-07 Last updated: 2019-10-07
Alonso, F., Zsigmond, P. & Wårdell, K. (2019). Influence of Virchow-Robin spaces in the Electric Field Distribution in Subthalamic Nucleus Deep Brain Stimulation. In: : . Paper presented at 18th Biennial meeting of the World Society for Stereotactic and Functional Neurosurgery. S. Karger
Open this publication in new window or tab >>Influence of Virchow-Robin spaces in the Electric Field Distribution in Subthalamic Nucleus Deep Brain Stimulation
2019 (English)Conference paper, Poster (with or without abstract) (Refereed)
Abstract [en]

Objectives: Previous investigations have shown the appearance of cysts i.e. Virchow-Robin spaces (VR) in the basal ganglia and their relationship with parkinsonian symptoms [1-3]. Simulations [4]using the finite element method (FEM) suggests that VR affects the electric field around deep brain stimulation (DBS) electrodes. The aim of the study was to evaluate how the electric field is modified by the presence of cysts in the STN. Methods: The effect of cysts on the electric field around the DBS lead placed in the STN was evaluated using FEM. 3D patient-specific brain models were built with COMSOL 5.2 (COMSOL AB, Sweden) and an in-house developed software [5] to convert a T2 weighted MRI of Parkinsonian patients (ethics approval no: 2012/434-3) into electrical conductivity matrix readable by FEM software. VR was classified as CSF [6]assigning a high electrical conductivity (2.0 S/m). The stimulation amplitudes were set to the clinically programmed values. Depending on the lead used, the stimulation was set to voltage control (3389) or current control (6180, ring mode). The coordinates corresponding to the lowest (first) electrode and the third higher up in the lead, taken from the postoperative CT electrode artefact, were used to localize the leads in the brain model [7]. The electric field was visualized with a 0.2V/mm isosurface. Results: Simulations showed that the electric field distribution is affected by the cysts. The higher conductivity at these regions in the vicinity of the electrode redistributes the electric field pushing it away from the cyst. The same effect occurs regardless of the operating mode or the lead design as long as the directional lead is configured in ring mode. Conclusions: The use of patient-specific models has shown the importance of considering nuances of the patients’ anatomy in the STN. This information can be used to determine the stimulation parameter and to support the analysis of side effects induced by the stimulation. The potential advantage of directional leads can also be assessed by including in the model patient-specific data.

Place, publisher, year, edition, pages
S. Karger, 2019
Series
Stereotact Funct Neurosurg 2019;97:1–560, ISSN 1011-6125, E-ISSN 1423-0372
National Category
Other Medical Engineering
Identifiers
urn:nbn:se:liu:diva-160751 (URN)
Conference
18th Biennial meeting of the World Society for Stereotactic and Functional Neurosurgery
Funder
Swedish Foundation for Strategic Research , BD15-0032
Available from: 2019-10-07 Created: 2019-10-07 Last updated: 2019-10-07
Johansson, J. D., Alonso, F. & Wårdell, K. (2019). Patient-Specific Simulations of Deep Brain Stimulation Electric Field with Aid of In-house Software ELMA. In: 2019 41st Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC): . Paper presented at The 41st International Engineering in Medicine and Biology Conference, Berlin, Germany, 23-27 July 2019. IEEE
Open this publication in new window or tab >>Patient-Specific Simulations of Deep Brain Stimulation Electric Field with Aid of In-house Software ELMA
2019 (English)In: 2019 41st Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), IEEE, 2019Conference paper, Published paper (Refereed)
Abstract [en]

Deep brain stimulation (DBS) is an established technique for reduction of symptoms in movement disorders. Finite element method (FEM) simulations of the electric field magnitude (EF) are useful for estimating the affected tissue around the DBS lead and this can help optimize the therapy. This paper describes how patient-specific FEM models can be set up with the aid of the Matlab-based in-house software tool ELMA. Electrode placement is determined from two coordinates in postoperative medical imaging and electric conductivity is assigned from preoperative magnetic resonance imaging (MRI) and patient-specific DBS data. Simulations are performed using the equation for steady currents in Comsol Multiphysics (CM). The simulated EF is superimposed on the preoperative MRI for evaluation of affected structures. The method is demonstrated with patient-specific simulations in the zona incerta and a globus pallidus example containing cysts with higher conductive which causes considerable distortion of the EF. The improved software modules and precise lead positioning simplifies and reduces the time for DBS EF modelling and simulation.

Place, publisher, year, edition, pages
IEEE, 2019
National Category
Medical Image Processing
Identifiers
urn:nbn:se:liu:diva-162290 (URN)10.1109/EMBC.2019.8856307 (DOI)
Conference
The 41st International Engineering in Medicine and Biology Conference, Berlin, Germany, 23-27 July 2019
Funder
Swedish Foundation for Strategic Research , BD15-0032Swedish Research Council, 2016-03564Knut and Alice Wallenberg Foundation, Seeing Organ Function
Available from: 2019-11-26 Created: 2019-11-26 Last updated: 2019-12-06Bibliographically approved
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: 2019-09-26Bibliographically 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
Show others...
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
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-6896-1452

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