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Åström, Mattias
Publications (10 of 37) Show all publications
Cubo, R., Medvedev, A. & Åström, M. (2016). Model-Based Optimization of Individualized Deep Brain Stimulation Therapy. IEEE DESIGN and TEST, 33(4), 74-81
Open this publication in new window or tab >>Model-Based Optimization of Individualized Deep Brain Stimulation Therapy
2016 (English)In: IEEE DESIGN and TEST, ISSN 2168-2356, Vol. 33, no 4, p. 74-81Article in journal (Refereed) Published
Abstract [en]

n/a

Place, publisher, year, edition, pages
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2016
National Category
Medical Biotechnology
Identifiers
urn:nbn:se:liu:diva-130399 (URN)10.1109/MDAT.2015.2480705 (DOI)000379598700008 ()
Note

Funding Agencies|European Research Council under Advanced Grant (ERC SysTEAM) [247035]

Available from: 2016-08-15 Created: 2016-08-05 Last updated: 2017-02-02Bibliographically approved
Wårdell, K., Kefalopoulou, Z., Diczfalusy, E., Andersson, M., Åström, M., Limousin, P., . . . Hariz, M. (2015). Deep Brain Stimulation of the Pallidum Internum for Gilles de la Tourette Syndrome: A Patient-Specific Model-Based Simulation Study of the Electric Field. Neuromodulation (Malden, Mass.) (2), 90-96
Open this publication in new window or tab >>Deep Brain Stimulation of the Pallidum Internum for Gilles de la Tourette Syndrome: A Patient-Specific Model-Based Simulation Study of the Electric Field
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2015 (English)In: Neuromodulation (Malden, Mass.), ISSN 1094-7159, E-ISSN 1525-1403, no 2, p. 90-96Article in journal (Refereed) Published
Abstract [en]

Objectives

The aim of this study was to investigate the deep brain stimulation (DBS) electric field distribution in proton-density MRI scans visualizing the globus pallidus internus (GPi) of patients with Gilles de la Tourette syndrome (GTS), along with its relation to the anatomy.

Methods

Patient-specific brain tissue models (n = 7) with bilateral DBS electrodes in the GPi were set up using the finite element method in five patients who had undergone stereotactic proton-density MRI-guided surgery and showed variable improvement with DBS. Simulations (n = 27) of the electric field were performed and the results visualized on the respective preoperative stereotactic MRI scans. The mean electric field volumes (n = 81) within the 0.1, 0.15, and 0.2 V/mm isosurfaces were calculated and compared with the anatomy.

Results

Visualization of the simulated electric field confirmed that the anteromedial limbic GPi was the main stimulated target for four of the patients and the posteromedial sensorimotor GPi for one. Larger volumes extended asymmetrically, with parts of fields stretching into the lamina between GPi and globus pallidus externus and into the internal capsule. There was a high correlation (r = 0.994, n = 54) between volumes and brain sides, but with a systematic shift toward the right side, especially for the larger volumes. Simulations with homogeneous tissue models showed no differences.

Conclusions

Patient-specific DBS electric field simulations in the GPi as visualized on proton-density MR scans can be implemented in patients with GTS. Visualization of electric fields together with stereotactic thin-slice MRI can provide further support when predicting anatomical structures possibly influenced by DBS in this complex disorder.

Place, publisher, year, edition, pages
John Wiley & Sons, 2015
Keywords
Deep brain stimulation, electric field simulation, globus pallidus internus, modeling and simulation, Tourette syndrome
National Category
Medical Biotechnology Medical Bioscience
Identifiers
urn:nbn:se:liu:diva-113589 (URN)10.1111/ner.12248 (DOI)000350461600004 ()25284508 (PubMedID)
Available from: 2015-01-23 Created: 2015-01-23 Last updated: 2017-12-05Bibliographically approved
Åström, M., Diczfalusy, E., Martens, H. & Wårdell, K. (2015). Relationship between Neural Activation and Electric Field Distribution during Deep Brain Stimulation. IEEE Transactions on Biomedical Engineering, 62(2), 664-72
Open this publication in new window or tab >>Relationship between Neural Activation and Electric Field Distribution during Deep Brain Stimulation
2015 (English)In: IEEE Transactions on Biomedical Engineering, ISSN 0018-9294, E-ISSN 1558-2531, Vol. 62, no 2, p. 664-72Article in journal (Refereed) Published
Abstract [en]

Models and simulations are commonly used to study deep brain stimulation (DBS). Simulated stimulation fields are often defined and visualized by electric field isolevels or volumes of tissue activated (VTA). The aim of the present study was to evaluate the relationship between stimulation field strength as defined by the electric potential V, the electric field E, and the divergence of the electric field ∇(2) V, and neural activation. Axon cable models were developed and coupled to finite-element DBS models in three-dimensional (3-D). Field thresholds ( VT , ET, and ∇(2) VT ) were derived at the location of activation for various stimulation amplitudes (1 to 5 V), pulse widths (30 to 120 μs), and axon diameters (2.0 to 7.5 μm). Results showed that thresholds for VT and ∇(2) VT were highly dependent on the stimulation amplitude while ET were approximately independent of the amplitude for large axons. The activation field strength thresholds presented in this study may be used in future studies to approximate the VTA during model-based investigations of DBS without the need of computational axon models.

Place, publisher, year, edition, pages
IEEE, 2015
National Category
Medical Bioscience Medical Biotechnology
Identifiers
urn:nbn:se:liu:diva-113588 (URN)10.1109/TBME.2014.2363494 (DOI)000348297000029 ()25350910 (PubMedID)
Note

This work was supported by the European Union's Seventh Framework Programme IMPACT (Grant 305814) and by the Swedish Research Council (Grant 621-2013-6078). Asterisk indicates corresponding author.

Available from: 2015-01-23 Created: 2015-01-23 Last updated: 2017-12-05Bibliographically approved
Åström, M. (2014). Functional brain atlas. 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 >>Functional brain atlas
2014 (English)Conference paper, Oral presentation only (Other academic)
National Category
Other Medical Engineering
Identifiers
urn:nbn:se:liu:diva-107600 (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
Åström, M. (2014). Neuronmodeling and DBS electric field simulations. 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 >>Neuronmodeling and DBS electric field simulations
2014 (English)Conference paper, Oral presentation only (Other academic)
National Category
Other Medical Engineering
Identifiers
urn:nbn:se:liu:diva-107603 (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
Wårdell, K., Åström, M., Diczfalusy, E. & Martens, H. (2014). Surgical Therapy: Parkinson's disease. In: Movement DisordersSupplement: Abstracts of the Eighteenth International Congress of Parkinson's Disease and Movement Disorders. Paper presented at The MDS 18th International Congress of Parkinson's Disease and Movement Disorders, June 8-12, 2014, Stockholm, Sweden (pp. 1170-1170). John Wiley & Sons, 29, Article ID Suppl 1:1170.
Open this publication in new window or tab >>Surgical Therapy: Parkinson's disease
2014 (English)In: Movement DisordersSupplement: Abstracts of the Eighteenth International Congress of Parkinson's Disease and Movement Disorders, John Wiley & Sons, 2014, Vol. 29, p. 1170-1170, article id Suppl 1:1170Conference paper, Poster (with or without abstract) (Other academic)
Abstract [en]

Objective: To analyze the relationship between the electric field and the volume of tissue activated (VTA) during model-based investigations of deep brain stimulation (DBS).

Background: An important factor for the therapeutic outcome of DBS is the spatial distribution of the stimulation field in the target area. Finite element models and simulations of DBS are increasingly being used to study the distribution of the stimulation field in relation to patient specific anatomy. The stimulation field is often defined as a VTA derived from computational axon models that are coupled to the finite element simulations. This approach however, is not feasible in many research centers due to the complexity of developing a computational axon model, as well as the extensive execution time when solving such models.

Methods: A detailed computer axon cable model was developed to study axonal activation in response to various DBS stimulation configurations. A range of axon models were set up and coupled to finite element models of DBS. DBS simulations were performed for Medtronic lead model 3389 during monopolar configurations for a range of amplitudes and pulse widths. Activation thresholds for the electric fields were derived by measuring the field strength at the maximum radius of activation for each configuration.

Results: Simulations showed that the electric field thresholds were related to stimulation amplitude, pulse width, and axon diameter. For large axons, the electric field threshold was not dependent on the amplitude, thus implying a low sensitivity of the electric field curvature.

Conclusions: Electric field thresholds can be used to predict the VTA during model-based investigations of DBS without the necessity of computer axon models. The use of electric field thresholds may substantially simplify the process of performing model-based investigations of DBS in the future.

Place, publisher, year, edition, pages
John Wiley & Sons, 2014
National Category
Other Medical Engineering
Identifiers
urn:nbn:se:liu:diva-107597 (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: 2017-02-13Bibliographically approved
Cubo, R., Åström, M. & Medvedev, A. (2014). Target coverage and selectivity in field steering brain stimulation. In: 2014 36TH ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC): . Paper presented at 36th Annual International Conference of the IEEE-Engineering-in-Medicine-and-Biology-Society (EMBC) (pp. 522-525). Institute of Electrical and Electronics Engineers (IEEE)
Open this publication in new window or tab >>Target coverage and selectivity in field steering brain stimulation
2014 (English)In: 2014 36TH ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC), Institute of Electrical and Electronics Engineers (IEEE), 2014, p. 522-525Conference paper, Published paper (Refereed)
Abstract [en]

Deep Brain Stimulation (DBS) is an established treatment in Parkinsons Disease. The target area is defined based on the state and brain anatomy of the patient. The stimulation delivered via state-of-the-art DBS leads that are currently in clinical use is difficult to individualize to the patient particularities. Furthermore, the electric field generated by such a lead has a limited selectivity, resulting in stimulation of areas adjacent to the target and thus causing undesirable side effects. The goal of this study is, using actual clinical data, to compare in silico the stimulation performance of a symmetrical generic lead to a more versatile and adaptable one allowing, in particular, for asymmetric stimulation. The fraction of the volume of activated tissue in the target area and the fraction of the stimulation field that spreads beyond it are computed for a clinical data set of patients in order to quantify the lead performance. The obtained results suggest that using more versatile DBS leads might reduce the stimulation area beyond the target and thus lessen side effects for the same achieved therapeutical effect.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2014
Series
IEEE Engineering in Medicine and Biology Society Conference Proceedings, ISSN 1557-170X, E-ISSN 1558-4615
National Category
Medical Biotechnology
Identifiers
urn:nbn:se:liu:diva-117398 (URN)10.1109/EMBC.2014.6943643 (DOI)000350044700130 ()25570011 (PubMedID)978-1-4244-7929-0 (ISBN)978-1-4244-7927-6 (ISBN)
Conference
36th Annual International Conference of the IEEE-Engineering-in-Medicine-and-Biology-Society (EMBC)
Available from: 2015-04-24 Created: 2015-04-24 Last updated: 2018-02-07Bibliographically approved
Wårdell, K., Diczfalusy, E., Åström, M. & Martens, H. (2013). Deep Brain Stimulation: Electric Field as a Predictor of Neural Activation. In: : . Paper presented at 6th Annual International IEEE EMBS Conference on Neural Engineering, San Diego, California, USA, 6 - 8 November.
Open this publication in new window or tab >>Deep Brain Stimulation: Electric Field as a Predictor of Neural Activation
2013 (English)Conference paper, Poster (with or without abstract) (Refereed)
National Category
Other Medical Engineering
Identifiers
urn:nbn:se:liu:diva-100834 (URN)
Conference
6th Annual International IEEE EMBS Conference on Neural Engineering, San Diego, California, USA, 6 - 8 November
Available from: 2013-11-13 Created: 2013-11-13 Last updated: 2017-02-03Bibliographically approved
Fytagoridis, A., Sjoberga, R. L., Åström, M., Fredricks, A., Nyberg, L. & Blomstedt, P. (2013). Effects of Deep Brain Stimulation in the Caudal Zona Incerta on Verbal Fluency. Stereotactic and Functional Neurosurgery, 91(1), 24-29
Open this publication in new window or tab >>Effects of Deep Brain Stimulation in the Caudal Zona Incerta on Verbal Fluency
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2013 (English)In: Stereotactic and Functional Neurosurgery, ISSN 1011-6125, E-ISSN 1423-0372, Vol. 91, no 1, p. 24-29Article in journal (Refereed) Published
Abstract [en]

Background: Deep brain stimulation (DBS) of the caudal zona incerta (cZi) is a relatively unexplored and promising treatment in patients with severe essential tremor (ET). Preliminary data further indicate that the ability to produce language may be slightly affected by the treatment. Objective: To evaluate the effects on verbal fluency following cZi DBS in patients with ET. Method: Seventeen consecutive patients who had undergone DBS of the cZi for ET were tested regarding verbal fluency before surgery, 3 days after surgery and after 1 year. Ten patients were also evaluated by comparing performance on versus off stimulation after 1 year. Results: The total verbal fluency score decreased slightly, but significantly, from 22.7 (SD = 10.9) before surgery to 18.1 (SD = 7.5) 3 days after surgery (p = 0.036). After 1 year the score was nonsignificantly decreased to 20.1 (SD = 9.7, p = 0.2678). There was no detectable difference between stimulation on and off after 1 year. Conclusion: There was a tendency of an immediate and mostly transient postoperative decline in verbal fluency following cZi DBS for ET. In some of the patients this reduction was, however, more pronounced and also sustained over time.

Place, publisher, year, edition, pages
Karger, 2013
Keywords
Deep brain stimulation, Verbal fluency, Essential tremor, Zona incerta, Posterior subthalamic area
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-89813 (URN)10.1159/000342497 (DOI)000314561100004 ()
Note

Funding Agencies|University of Umea||Foundation for Clinical Neuroscience at the University Hospital of Umea||

Available from: 2013-03-07 Created: 2013-03-07 Last updated: 2017-12-06Bibliographically approved
Fytagoridis, A., Åström, M., Wårdell, K. & Blomstedt, P. (2013). Stimulation-induced side effects in the posterior subthalamic area: distribution, characteristics and visualization. Clinical neurology and neurosurgery (Dutch-Flemish ed. Print), 15(1), 65-71
Open this publication in new window or tab >>Stimulation-induced side effects in the posterior subthalamic area: distribution, characteristics and visualization
2013 (English)In: Clinical neurology and neurosurgery (Dutch-Flemish ed. Print), ISSN 0303-8467, E-ISSN 1872-6968, Vol. 15, no 1, p. 65-71Article in journal (Refereed) Published
Abstract [en]

Objective: The posterior subthalamic area (PSA) is an emerging but relatively unexplored target for DBS treatment of tremor. The aim of the study was to explore the area further by evaluating the spatial distribution and the characteristics of stimulation-induced side effects in this area. Methods: Twenty-eight patients with essential tremor (ET) implanted with 33 DBS electrodes were evaluated concerning stimulation-induced side effects by testing each contact separately one year after surgery. The location of the side effects were plotted on axial slides of the Morel Stereotactic Atlas and a 3-dimensional model of the area for visualization was created. Results: Visualization of the contacts eliciting stimulation-induced side effects demonstrated that identical responses can be elicited from various points in the PSA and its vicinity. The majority of contacts inducing muscular affection and cerebellar symptoms, including dysarthria, could not be attributed to an effect on the internal capsule. Paresthesias, affecting various body parts were elicited throughout the area without a clear somatotopic pattern. Conclusion: Stimulation-induced side effects in the PSA and its vicinity are difficult to attribute to certain anatomical areas as the same response can be induced from various locations, and are thus of limited localizing value.

Place, publisher, year, edition, pages
Elsevier, 2013
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-70088 (URN)10.1016/j.clineuro.2012.04.015 (DOI)000312576300012 ()
Available from: 2011-08-18 Created: 2011-08-18 Last updated: 2017-12-08Bibliographically approved
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