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Latorre, M. & Wårdell, K. (2019). A comparison between single and double cable neuron models applicable to deep brain stimulation. Biomedical Physics & Engineering Express, 5(2)
Öppna denna publikation i ny flik eller fönster >>A comparison between single and double cable neuron models applicable to deep brain stimulation
2019 (Engelska)Ingår i: Biomedical Physics & Engineering Express, E-ISSN 2057-1976, Vol. 5, nr 2Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Computational models for activation assessment in deep brain stimulation (DBS) are commonly based on neuronal cable equations. The aim was to systematically compare the activation distance between a single cable model implemented in MATLAB, and a well-established double cable model implemented in NEURON. Both models have previously been used for DBS studies. The field distributions generated from a point source and a 3389 DBS lead were applied to the neuron models as input stimuli. Simulations (n = 670) were performed with intersecting axon diameters (D) between the models (2.0, 3.0, 5.7, 7.3, 8.7, 10.0 μm), variation in pulse shape and amplitude settings (0 to 5 in increments of 0.5 mA or V) with the single cable model as reference. Both models responded linearly to change of input (point source: 0.93 < R2 < 0.99, DBS source: R2 > 0.98), but with a systematic extended activation distance for the single cable model. The difference for a point source ranged from −0.2 mm (D = 2.0 μm) to −1.1 mm (D = 5.7 μm). For the DBS lead a D = 3.2 μm agreed with the commonly used double cable simulations D =5.7 μm in voltage mode. Possible reasons for the deviation at larger axons are the internodal length, the ion channel selection and physiological data behind the models. The single cable model covers a continuous range of small axon diameters and calculated the internodal length for each iteration, whereas the double cable models uses fixed defined axon diameters and tabulated data for the internodal length. Despite different implementations and model complexities, both models present similar sensitivity to pulse shape, amplitude and axon diameter. With awareness of the strength and weakness both models can be used to extract activation distance used to relate a specific electric field isolevel and thus estimate the volume of tissue activated in DBS simulation studies.

Ort, förlag, år, upplaga, sidor
Bibliopolis, Edizioni di Filosofia e Scienze, 2019
Nationell ämneskategori
Medicinteknik
Identifikatorer
urn:nbn:se:liu:diva-155800 (URN)10.1088/2057-1976/aafdd9 (DOI)000487519600015 ()
Anmärkning

Funding agencies: Swedish Foundation [BD15-0032]; Swedish Research CouncilSwedish Research Council [2016-03564]

Tillgänglig från: 2019-03-28 Skapad: 2019-03-28 Senast uppdaterad: 2019-11-04
Pham, T. (2019). Classification of Short Time Series in Early Parkinson’s Disease With Deep Learning of Fuzzy Recurrence Plots. IEEE/CAA Journal of Automatica Sinica
Öppna denna publikation i ny flik eller fönster >>Classification of Short Time Series in Early Parkinson’s Disease With Deep Learning of Fuzzy Recurrence Plots
2019 (Engelska)Ingår i: IEEE/CAA Journal of Automatica SinicaArtikel i tidskrift (Refereegranskat) Published
Abstract [en]

There are many techniques using sensors and wearable devices for detecting and monitoring patients with Parkinson's disease (PD). A recent development is the utilization of human interaction with computer keyboards for analyzing and identifying motor signs in the early stages of the disease. Current designs for classification of time series of computer-key hold durations recorded from healthy control and PD subjects require the time series of length to be considerably long. With an attempt to avoid discomfort to participants in performing long physical tasks for data recording, this paper introduces the use of fuzzy recurrence plots of very short time series as input data for the machine training and classification with long short-term memory (LSTM) neural networks. Being an original approach that is able to both significantly increase the feature dimensions and provides the property of deterministic dynamical systems of very short time series for information processing carried out by an LSTM layer architecture, fuzzy recurrence plots provide promising results and outperform the direct input of the time series for the classification of healthy control and early PD subjects.

Nyckelord
Deep learning, early Parkinson’s disease (PD), fuzzy recurrence plots, long short-term memory (LSTM) neural networks, pattern classification, short time series
Nationell ämneskategori
Medicinteknik
Identifikatorer
urn:nbn:se:liu:diva-161818 (URN)10.1109/JAS.2019.1911774 (DOI)
Tillgänglig från: 2019-11-11 Skapad: 2019-11-11 Senast uppdaterad: 2019-11-11
Nordin, T., Stenmark Persson, R., Blomstedt, P. & Wårdell, K. (2019). Improvement Maps for Deep Brain Stimulation in Parkinson’s Disease. In: : . Paper presented at 41st Annual International Conference of the IEEE Engineering in Medicine and Biology Society Berlin.
Öppna denna publikation i ny flik eller fönster >>Improvement Maps for Deep Brain Stimulation in Parkinson’s Disease
2019 (Engelska)Konferensbidrag, Poster (med eller utan abstract) (Övrigt vetenskapligt)
Nationell ämneskategori
Medicinteknik
Identifikatorer
urn:nbn:se:liu:diva-160833 (URN)
Konferens
41st Annual International Conference of the IEEE Engineering in Medicine and Biology Society Berlin
Tillgänglig från: 2019-10-10 Skapad: 2019-10-10 Senast uppdaterad: 2019-10-10
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
Öppna denna publikation i ny flik eller fönster >>Influence of Virchow-Robin spaces in the Electric Field Distribution in Subthalamic Nucleus Deep Brain Stimulation
2019 (Engelska)Konferensbidrag, Poster (med eller utan abstract) (Refereegranskat)
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.

Ort, förlag, år, upplaga, sidor
S. Karger, 2019
Serie
Stereotact Funct Neurosurg 2019;97:1–560, ISSN 1011-6125, E-ISSN 1423-0372
Nationell ämneskategori
Annan medicinteknik
Identifikatorer
urn:nbn:se:liu:diva-160751 (URN)
Konferens
18th Biennial meeting of the World Society for Stereotactic and Functional Neurosurgery
Forskningsfinansiär
Stiftelsen för strategisk forskning (SSF), BD15-0032
Tillgänglig från: 2019-10-07 Skapad: 2019-10-07 Senast uppdaterad: 2019-10-07
Haj-Hosseini, N., Richter, J., Milos, P., Hallbeck, M. & Wårdell, K. (2018). 5-ALA fluorescence and laser Doppler flowmetry for guidance in a stereotactic brain tumor biopsy. Biomedical Optics Express, 9(5), 2284-2296
Öppna denna publikation i ny flik eller fönster >>5-ALA fluorescence and laser Doppler flowmetry for guidance in a stereotactic brain tumor biopsy
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2018 (Engelska)Ingår i: Biomedical Optics Express, E-ISSN 2156-7085, Vol. 9, nr 5, s. 2284-2296Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

A fiber optic probe was developed for guidance during stereotactic brain biopsy procedures to target tumor tissue and reduce the risk of hemorrhage. The probe was connected to a setup for the measurement of 5-aminolevulinic acid (5-ALA) induced fluorescence and microvascular blood flow. Along three stereotactic trajectories, fluorescence (n = 109) and laser Doppler flowmetry (LDF) (n = 144) measurements were done in millimeter increments. The recorded signals were compared to histopathology and radiology images. The median ratio of protoporphyrin IX (PpIX) fluorescence and autofluorescence (AF) in the tumor was considerably higher than the marginal zone (17.3 vs 0.9). The blood flow showed two high spots (3%) in total. The proposed setup allows simultaneous and real-time detection of tumor tissue and microvascular blood flow for tracking the vessels.

Ort, förlag, år, upplaga, sidor
Optical Society of America, 2018
Nationell ämneskategori
Medicinteknik
Identifikatorer
urn:nbn:se:liu:diva-147514 (URN)10.1364/BOE.9.002284 (DOI)000431181700022 ()29760987 (PubMedID)
Forskningsfinansiär
Barncancerfonden, 2013-0043Linköpings universitet, LiU CancerRegion Östergötland, ALF LIO-599651
Anmärkning

Funding agencies: Linkoping University Cancer Organization; Swedish Childhood Cancer Organization [MT 2013-0043]; ALF Grants Region Ostergotland [LIO-599651]

Tillgänglig från: 2018-04-23 Skapad: 2018-04-23 Senast uppdaterad: 2019-10-14Bibliografiskt granskad
Nordin, T., Zsigmond, P., Pujol, S., Westin, C.-F. & Wårdell, K. (2018). Computer models in deep brain stimulation based on diffusion MRI. In: : . Paper presented at Medicinteknikdagarna, 9-10 oktober 2018, Umeå, Sverige.
Öppna denna publikation i ny flik eller fönster >>Computer models in deep brain stimulation based on diffusion MRI
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2018 (Engelska)Konferensbidrag, Enbart muntlig presentation (Refereegranskat)
Nationell ämneskategori
Medicinteknik
Identifikatorer
urn:nbn:se:liu:diva-152025 (URN)
Konferens
Medicinteknikdagarna, 9-10 oktober 2018, Umeå, Sverige
Tillgänglig från: 2018-10-17 Skapad: 2018-10-17 Senast uppdaterad: 2018-10-17
Nordin, T., Zsigmond, P., Pujol, S., Westin, C.-F. & Wårdell, K. (2018). Deep brain stimulation: Patient-specific electrical field simulation. In: : . Paper presented at XXIIIrd congress of the European Society for Stereotactic and Functional Neurosurgery, 26-29 september 2018, Edinburgh, Scotland (ESSFN).
Öppna denna publikation i ny flik eller fönster >>Deep brain stimulation: Patient-specific electrical field simulation
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2018 (Engelska)Konferensbidrag, Muntlig presentation med publicerat abstract (Refereegranskat)
Nationell ämneskategori
Medicinteknik
Identifikatorer
urn:nbn:se:liu:diva-152027 (URN)
Konferens
XXIIIrd congress of the European Society for Stereotactic and Functional Neurosurgery, 26-29 september 2018, Edinburgh, Scotland (ESSFN)
Tillgänglig från: 2018-10-17 Skapad: 2018-10-17 Senast uppdaterad: 2018-10-17
Wårdell, K., Zsigmond, P., Richter, J. & Hemm, S. (2018). Optical Guidance System for Deep Brain Stimulation Surgery: from Experimental Studies to Clinical Use. In: : . Paper presented at Biophotonics Congress: Biomedical Optics Congress, The Diplomat Beach Resort, Hollywood, Florida USA, 3–6 April 2018. Hollywood, Florida, United States, Article ID CTh2B.3.
Öppna denna publikation i ny flik eller fönster >>Optical Guidance System for Deep Brain Stimulation Surgery: from Experimental Studies to Clinical Use
2018 (Engelska)Ingår i: , Hollywood, Florida, United States, 2018, artikel-id CTh2B.3Konferensbidrag, Muntlig presentation med publicerat abstract (Refereegranskat)
Abstract [en]

Laser Doppler flowmetry (LDF) has been adapted for optical guidance during stereotactic deep brain stimulation (DBS) surgery. It has been used in more than 130 DBS implantations. The necessary steps to go from experimental studies to clinical use in the neurosurgical setting are reviewed.

Ort, förlag, år, upplaga, sidor
Hollywood, Florida, United States: , 2018
Serie
(Microscopy/Translational/Brain/OTS)
Nationell ämneskategori
Annan medicinteknik
Identifikatorer
urn:nbn:se:liu:diva-147678 (URN)10.1364/TRANSLATIONAL.2018.CTh2B.3 (DOI)978-1-943580-41-5 (ISBN)
Konferens
Biophotonics Congress: Biomedical Optics Congress, The Diplomat Beach Resort, Hollywood, Florida USA, 3–6 April 2018
Forskningsfinansiär
Vetenskapsrådet, 621-2013-6078Stiftelsen för strategisk forskning (SSF), BD15-0032
Tillgänglig från: 2018-05-04 Skapad: 2018-05-04 Senast uppdaterad: 2018-05-15Bibliografiskt granskad
Haj-Hosseini, N., Richter, J., Hallbeck, M., Milos, P. & Wårdell, K. (2018). Stereotactic Brain Tumor Optical Biopsy. In: : . Paper presented at World Conference on Medical Physics and Biomedical Engineering (IUPESM,Prague, Czeck Republic, June 3-8 2018. Prague
Öppna denna publikation i ny flik eller fönster >>Stereotactic Brain Tumor Optical Biopsy
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2018 (Engelska)Konferensbidrag, Muntlig presentation med publicerat abstract (Övrigt vetenskapligt)
Abstract [en]

To provide guidance for targeting diagnostic tumor tissue and to avoid vessel rupture during the biopsy procedure an application specific fiber optic probe was devel-oped. The setup incorporated an in-house developed fluorescence spectroscopy system for 5-aminolevulinic acid (5-ALA) induced protopophyrin IX (PpIX) for detection in the tumor, and laser Doppler flowmeter (LDF) system for measurement of blood perfusion. Fluorescence and blood flow were recorded millimeter-wise towards the pre-calculated target. In conclusion, the optical probe made real-time detection of tumor possible and has a potential for vessel detection during the biopsy procedures. Moreover, the PpIX fluorescence, autofluorescence and blood flow in the tumor could be studied at precise positions in the brain and the tumor. In the next step, further anal-ysis will be added.

Ort, förlag, år, upplaga, sidor
Prague: , 2018
Nationell ämneskategori
Annan medicinteknik
Identifikatorer
urn:nbn:se:liu:diva-145220 (URN)
Konferens
World Conference on Medical Physics and Biomedical Engineering (IUPESM,Prague, Czeck Republic, June 3-8 2018
Forskningsfinansiär
Barncancerfonden, MT 2013-0043
Tillgänglig från: 2018-02-19 Skapad: 2018-02-19 Senast uppdaterad: 2019-10-14Bibliografiskt granskad
Rejmstad, P., Johansson, J. D., Haj-Hosseini, N. & Wårdell, K. (2017). A method for monitoring of oxygen saturation changes in brain tissue using diffuse reflectance spectroscopy. Journal of Biophotonics, 10(3), 446-455
Öppna denna publikation i ny flik eller fönster >>A method for monitoring of oxygen saturation changes in brain tissue using diffuse reflectance spectroscopy
2017 (Engelska)Ingår i: Journal of Biophotonics, ISSN 1864-063X, E-ISSN 1864-0648, Vol. 10, nr 3, s. 446-455Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Continuous measurement of local brain oxygen saturation (SO2) can be used to monitor the status of brain trauma patients in the neurocritical care unit. Currently, micro-oxygen-electrodes are considered as the “gold standard” in measuring cerebral oxygen pressure (pO2), which is closely related to SO2 through the oxygen dissociation curve (ODC) of hemoglobin, but with the drawback of slow in response time. The present study suggests estimation of SO2 in brain tissue using diffuse reflectance spectroscopy (DRS) for finding an analytical relation between measured spectra and the SO2 for different blood concentrations. The P3 diffusion approximation is used to generate a set of spectra simulating brain tissue for various levels of blood concentrations in order to estimate SO2. The algorithm is evaluated on optical phantoms mimicking white brain matter (blood volume of 0.5–2%) where pO2 and temperature is controlled and on clinical data collected during brain surgery. The suggested method is capable of estimating the blood fraction and oxygen saturation changes from the spectroscopic signal and the hemoglobin absorption profile.

Ort, förlag, år, upplaga, sidor
Wiley-VCH Verlagsgesellschaft, 2017
Nyckelord
oxygenation, diffuse reflectance spectroscopy, hemoglobin, optical phantom, human brain
Nationell ämneskategori
Annan medicinteknik
Identifikatorer
urn:nbn:se:liu:diva-127362 (URN)10.1002/jbio.201500334 (DOI)000398216200012 ()27094015 (PubMedID)
Anmärkning

Funding agencies: Swedish Childhood Cancer Foundation; Swedish Research Council [621-2010-4216, 621-2013-6078]

Tillgänglig från: 2016-04-22 Skapad: 2016-04-22 Senast uppdaterad: 2017-04-20Bibliografiskt granskad
Organisationer
Identifikatorer
ORCID-id: ORCID iD iconorcid.org/0000-0002-0012-7867

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