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  • 1.
    Akbarian-Tefaghi, Ladan
    et al.
    Unit of Functional Neurosurgery, Sobell Department of Motor Neuroscience, UCL Institute of Neurology, London, UK.
    Akram, Harith
    Unit of Functional Neurosurgery, Sobell Department of Motor Neuroscience, UCL Institute of Neurology, London, UK.
    Johansson, Johannes
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
    Zrinzo, Ludvic
    Unit of Functional Neurosurgery, Sobell Department of Motor Neuroscience, UCL Institute of Neurology, London, UK.
    Kefalopoulou, Zinovia
    Unit of Functional Neurosurgery, Sobell Department of Motor Neuroscience, UCL Institute of Neurology, London, UK.
    Limousin, Patricia
    Unit of Functional Neurosurgery, Sobell Department of Motor Neuroscience, UCL Institute of Neurology, London, UK.
    Joyce, Eileen
    Unit of Functional Neurosurgery, Sobell Department of Motor Neuroscience, UCL Institute of Neurology, London, UK.
    Hariz, Marwan
    Unit of Functional Neurosurgery, Sobell Department of Motor Neuroscience, UCL Institute of Neurology, London, UK.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
    Foltynie, Tom
    Unit of Functional Neurosurgery, Sobell Department of Motor Neuroscience, UCL Institute of Neurology, London, UK.
    Refining the Deep Brain Stimulation Target within the Limbic Globus Pallidus Internus for Tourette Syndrome2017In: Stereotactic and Functional Neurosurgery, ISSN 1011-6125, E-ISSN 1423-0372, Vol. 95, no 4, p. 251-258Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Deep brain stimulation (DBS) in patients with severe, refractory Tourette syndrome (TS) has demonstrated promising but variable results thus far. The thalamus and anteromedial globus pallidus internus (amGPi) have been the most commonly stimulated sites within the cortico-striato thalamic circuit, but an optimal target is yet to be elucidated.

    OBJECTIVES: This study of 15 patients with long-term amGPi DBS for severe TS investigated whether a specific anatomical site within the amGPi correlated with optimal clinical outcome for the measures of tics, obsessive compulsive behaviour (OCB), and mood.

    METHODS: Validated clinical assessments were used to measure tics, OCB, quality of life, anxiety, and depression before DBS and at the latest follow-up (17-82 months). Electric field simulations were created for each patient using information on electrode location and individual stimulation parameters. A subsequent regression analysis correlated these patient-specific simulations to percentage changes in outcome measures in order to identify any significant voxels related to clinical improvement.

    RESULTS: A region within the ventral limbic GPi, specifically on the medial medullary lamina in the pallidum at the level of the AC-PC, was significantly associated with improved tics but not mood or OCB outcome.

    CONCLUSIONS: This study adds further support to the application of DBS in a tic-related network, though factors such as patient sample size and clinical heterogeneity remain as limitations and replication is required.

  • 2. Eriksson, O.
    et al.
    Johansson, Johannes
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Finite element simulations of rf lesions in porcine brain2002Conference paper (Refereed)
  • 3.
    Göransson, Nathanael
    et al.
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
    Johansson, Johannes
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
    Alonso, Fabiola
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
    Zsigmond, Peter
    Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Anaesthetics, Operations and Specialty Surgery Center, Department of Neurosurgery.
    Postoperative lead movement after deep brain stimulation surgery and changes of stimulation area2017Conference paper (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.

  • 4.
    Han, Songfeng
    et al.
    Institute of Optics, University of Rochester.
    Johansson, Johannes
    ICFO- Institut de Ciències Fotòniques.
    Mireles, Miguel
    ICFO- Institut de Ciències Fotòniques.
    Proctor, Ashley R
    Department of Biomedical Engineering, University of Rochester.
    Hoffman, Michael D
    Department of Biomedical Engineering, University of Rochester.
    Vella, Joseph B
    Department of Biomedical Engineering, University of Rochester.
    Benoit, Danielle S W
    Department of Biomedical Engineering, University of Rochester.
    Durduran, Turgut
    ICFO- Institut de Ciències Fotòniques.
    Choe, Regine
    Department of Biomedical Engineering, University of Rochester.
    Non-contact scanning diffuse correlation tomography system for three-dimensional blood flow imaging in a murine bone graft model.2015In: Biomedical Optics Express, ISSN 2156-7085, E-ISSN 2156-7085, Vol. 6, no 7Article in journal (Refereed)
    Abstract [en]

    A non-contact galvanometer-based optical scanning system for diffuse correlation tomography was developed for monitoring bone graft healing in a murine femur model. A linear image reconstruction algorithm for diffuse correlation tomography was tested using finite-element method based simulated data and experimental data from a femur or a tube suspended in a homogeneous liquid phantom. Finally, the non-contact system was utilized to monitor in vivo blood flow changes prior to and one week after bone graft transplantation within murine femurs. Localized blood flow changes were observed in three mice, demonstrating a potential for quantification of longitudinal blood flow associated with bone graft healing.

  • 5.
    Johansson, Johannes
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Impact of Tissue Characteristics on Radio-Frequency Lesioning and Navigation in the Brain: Simulation, experimental and clinical studies2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Radio-Frequency (RF) lesioning, or RF ablation, is a method that uses high frequency currents for thermal coagulation of pathological tissue or signal pathways. The current is delivered from an electrode, which also contains a temperature sensor permitting control of the current at a desired target temperature. In the brain, RF lesioning can e.g. be used for treatment of severe chronic pain and movement disorders such as Parkinson’s disease. This thesis focuses on modelling and simulation with the aim of gaining better understanding and predictability of the lesioning process in the central brain.

     

    The finite element method (FEM), together with experimental comparisons, was used to study the effects of electric and thermal conductivity, blood perfusion (Paper I), and cerebrospinal fluid (CSF) filled cysts (Paper II) on resulting lesion volume and shape in brain tissue. The influence of blood perfusion was modelled as an increase in thermal conductivity in non-coagulated tissue. This model gave smaller simulated lesions with increasing blood perfusion as heat was more efficiently conducted from the rim of the lesion. If the coagulation was not taken into consideration, the lesion became larger with increasing thermal conductivity instead, as the increase in conducted heat was compensated for through an increased power output in order to maintain the target temperature. Simulated lesions corresponded well to experimental in-vivo lesions. The electric conductivity in a homogeneous surrounding had little impact but this was not true for a heterogeneous surrounding. CSF has a much higher electric conductivity than brain tissue, which focused the current to the cyst if the electrode tip was in contact with both a cyst and brain tissue. Heating of CSF could also cause considerable convective flow and as a result a very efficient heat transfer. This affected both simulated and experimental lesion sizes and shapes. As a result both very large and very small lesions could be obtained depending on whether sufficient power was supplied or if the heating was mitigated over a large volume.

     

    Clinical (Paper IV) and experimental (Paper III) measurements were used for investigation of changes in reflected light intensity from undamaged and coagulating brain tissue respectively. Monte Carlo (MC) simulations for light transport were made for comparison (Paper V). For the optical measurements, an RF electrode with adjacent optical fibres was used and this electrode was also modelled for the optical simulations. According to the MC simulations, coagulation should make grey matter lighter and white matter darker, while thalamic light grey should remain approximately the same. Experiments in ex-vivo porcine tissue gave an increase in reflected light intensity from grey matter at approximately 50 °C but the signal was very variable and the isotherm 60 °C gave better agreement between simulated and experimental lesions. No consistent decrease in reflected light intensity could be seen during coagulation of white matter. Clinical measurements were performed during the creation of 21 trajectories for deep brain stimulation electrodes. In agreement with the simulations, reflected light intensity was found to differentiate well between undamaged grey, light grey and white matter.

     

    In conclusion, blood perfusion and CSF in particular may greatly affect the lesioning process and can be important to consider when planning surgery. Reflected light intensity seems unreliable for the detection of coagulation in light grey brain matter such as the thalamus. However, it seems very promising for navigation in the brain and for detection of coagulation in other tissue types such as muscle.

    List of papers
    1. Radio-frequency lesioning in brain tissue with coagulation-dependent thermal conductivity: modelling, simulation and analysis of parameter influence and interaction
    Open this publication in new window or tab >>Radio-frequency lesioning in brain tissue with coagulation-dependent thermal conductivity: modelling, simulation and analysis of parameter influence and interaction
    Show others...
    2006 (English)In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 44, no 9, p. 757-766Article in journal (Refereed) Published
    Abstract [en]

    Radio-frequency brain lesioning is a method for reducing e.g. symptoms of movement disorders. A small electrode is used to thermally coagulate malfunctioning tissue. Influence on lesion size from thermal and electric conductivity of the tissue, microvascular perfusion and preset electrode temperature was investigated using a finite-element model. Perfusion was modelled as an increased thermal conductivity in non-coagulated tissue. The parameters were analysed using a 24-factorial design (n = 16) and quadratic regression analysis (n = 47). Increased thermal conductivity of the tissue increased lesion volume, while increased perfusion decreased it since coagulation creates a thermally insulating layer due to the cessation of blood perfusion. These effects were strengthened with increased preset temperature. The electric conductivity had negligible effect. Simulations were found realistic compared to in vivo experimental lesions.

    Place, publisher, year, edition, pages
    Heidleberg: Springer, 2006
    Keywords
    Electrosurgery, RF ablation, Brain, Blood perfusion, Finite-element method
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-15926 (URN)10.1007/s11517-006-0098-1 (DOI)000240378700003 ()16941099 (PubMedID)2-s2.0-33748485613 (Scopus ID)
    Note

    The original publication is available at www.springerlink.com: Johannes D Johansson, Ola Eriksson, Joakim Wren, Dan Loyd and Karin Wårdell, Radio-frequency lesioning in brain tissue with coagulation-dependent thermal conductivity: modelling, simulation and analysis of parameter influence and interaction, 2006, Medical and Biological Engineering and Computing, (44), 9, 757-766. http://dx.doi.org/10.1007/s11517-006-0098-1 Copyright: Springer Science Business Media http://www.springerlink.com/

    Available from: 2008-12-16 Created: 2008-12-16 Last updated: 2017-12-14Bibliographically approved
    2. Impact of cysts during radio frequency (RF) lesioning in deep brain structures: a simulation and in-vitro study
    Open this publication in new window or tab >>Impact of cysts during radio frequency (RF) lesioning in deep brain structures: a simulation and in-vitro study
    2007 (English)In: Journal of Neural Engineering, ISSN 1741-2560, E-ISSN 1741-2552, Vol. 4, no 2, p. 87-95Article in journal (Refereed) Published
    Abstract [en]

    Radiofrequency lesioning of nuclei in the thalamus or the basal ganglia can be used to reduce symptoms caused by e.g. movement disorders such as Parkinson's disease. Enlarged cavities containing cerebrospinal fluid (CSF) are commonly present in the basal ganglia and tend to increase in size and number with age. Since the cavities have different electrical and thermal properties compared with brain tissue, it is likely that they can affect the lesioning process and thereby the treatment outcome. Computer simulations using the finite element method and in vitro experiments have been used to investigate the impact of cysts on lesions' size and shape. Simulations of the electric current and temperature distributions as well as convective movements have been conducted for various sizes, shapes and locations of the cysts as well as different target temperatures. Circulation of the CSF caused by the heating was found to spread heat effectively and the higher electric conductivity of the CSF increased heating of the cyst. These two effects were together able to greatly alter the resulting lesion size and shape when the cyst was in contact with the electrode tip. Similar results were obtained for the experiments.

    Place, publisher, year, edition, pages
    Institute of Physics Publishing (IOPP), 2007
    Keywords
    Electrosurgery, RF ablation, Brain, Blood perfusion, Finite-element method
    National Category
    Other Medical Engineering
    Identifiers
    urn:nbn:se:liu:diva-13997 (URN)10.1088/1741-2560/4/2/009 (DOI)000247947300015 ()17409483 (PubMedID)2-s2.0-34247183212 (Scopus ID)
    Note

    Original Publication: Johannes D. Johansson, Dan Loyd, Karin Wårdell and Joakim Wren, Impact of cysts during radio frequency (RF) lesioning in deep brain structures: a simulation and in-vitro study, 2006, Journal of Neural Ingeneering, (4), 2, 87-95. http://dx.doi.org/10.1088/1741-2560/4/2/009 Copyright: Institute of Physics Publishing http://www.iop.org/

    Available from: 2008-12-16 Created: 2008-12-16 Last updated: 2017-12-13Bibliographically approved
    3. Diffuse Reflectance Spectroscopy During Experimental Radio Frequency Ablation
    Open this publication in new window or tab >>Diffuse Reflectance Spectroscopy During Experimental Radio Frequency Ablation
    2008 (English)In: 14th Nordic-Baltic Conference on Biomedical Engineering and Medical Physics: NBC 2008 16–20 June 2008 Riga, Latvia / [ed] Alexei Katashev, Yuri Dekhtyar, Janis Spigulis, Heidelberg: Springer Berlin/Heidelberg, 2008, p. 371-374Chapter in book (Refereed)
    Abstract [en]

    The aim of the study was to investigate the spectral changes during heating and to estimate threshold temperatures for initiation of the thermal coagulation. A brain electrode with optical fibers was used to generate lesions in ex-vivo porcine white and gray matter as well as in fat and meat from pork chop. Radio frequency ablation (60 s, 48–90 °C, steps of 2-10 °C) was performed while simultaneous spectroscopy measurements were made in the range 490–900 nm.

    The optical signal recorded from porcine gray and white brain matter was unstable with the reflected light intensity fluctuating a lot. Nevertheless an abrupt increase in light intensity during coagulation in gray matter was found at 48 ± 6 °C (n = 21), probably indicating onset of coagulation. The reflected light intensity from white matter showed no consistent behavior during coagulation.

    The results for pork chop meat and fat were considerably more consistent. The reflected light intensity from pork chop meat stayed stable up to a mean temperature of 42.5 ± 3.5 °C (n = 11). Above this temperature it abruptly increased for all wavelengths. The reflected light intensity from pork chop fat dropped over all wavelengths immediately as the temperature increased and remained low as the fat cooled (n = 8).

    In conclusion diffuse reflectance spectroscopy appears to be suitable to detect onset of coagulation in muscle tissue and gray matter. The estimated initiation temperature of coagulation varied and was dependent on tissue type.

    Place, publisher, year, edition, pages
    Heidelberg: Springer Berlin/Heidelberg, 2008
    Series
    IFMBE Proceedings, ISSN 1680-0737 ; 20
    Keywords
    Radio frequency ablation, diffuse reflectance spectroscopy, brain, muscle, fat
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-15927 (URN)10.1007/978-3-540-69367-3_99 (DOI)978-3-540-69366-6 (ISBN)978-3-540-69367-3 (ISBN)
    Available from: 2008-12-16 Created: 2008-12-16 Last updated: 2017-02-16Bibliographically approved
    4. Combined diffuse light reflectance and electric impedance measurements for navigation aid in deep brain surgery
    Open this publication in new window or tab >>Combined diffuse light reflectance and electric impedance measurements for navigation aid in deep brain surgery
    Show others...
    2009 (English)In: Stereotactic and Functional Neurosurgery, ISSN 1011-6125, E-ISSN 1423-0372, Vol. 87, no 2, p. 105-113Article in journal (Refereed) Published
    Abstract [en]

    Aim: The aim of this study is to investigate reflected light intensity combined with impedance for navigation aid during stereotactic neurosurgery.

    Methods: During creation of 21 trajectories for stereotactic implantation of deep brain stimulation electrodes in the globus pallidus internus or subthalamus (zona incerta or subthalamic nucleus), impedance at 512 kHz and reflected light intensity at 780 nm were measured continuously and simultaneously with a radio frequency electrode containing optical fibres. The signals were compared with anatomy determined from pre- and postoperative MRI and CT. The measurements were performed within minutes and signal analysis was done post-operatively.

    Results: Reflected light intensity was low from cortex, lateral ventricle, caudate nucleus and putamen. It was intermediate from globus pallidus and thalamus while it was high from subcortical white matter, internal capsule and the subthalamus. The electric impedance was less consistent but generally low in the cortex, intermediate in subcortical white matter, the putamen, the globus pallidus and the thalamus and high in the internal capsule and the subthalamus.

    Conclusion: Reflected light intensity and electric impedance give complementary information about passed tissue and the combination seems promising for navigation aid during stereotactic neurosurgery.

    Keywords
    Stereotactic surgery, navigation, electric impedance, light reflectance
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-15929 (URN)10.1159/000202977 (DOI)
    Note

    Original Publication: Johannes D. Johansson, Patric Blomstedt, Neda Haj-Hosseini, Tommy Bergenheim, Ola Eriksson and Karin Wårdell, Combined diffuse light reflectance and electric impedance measurements for navigation aid in deep brain surgery, 2009, Stereotactic and Functional Neurosurgery, (87), 2, 105-113. http://dx.doi.org/10.1159/000202977 Copyright: S. Karger AG http://www.karger.com/

    Available from: 2008-12-16 Created: 2008-12-16 Last updated: 2017-12-14Bibliographically approved
    5. Simulation of reflected light intensity changes during navigation and radio frequency lesioning in the brain
    Open this publication in new window or tab >>Simulation of reflected light intensity changes during navigation and radio frequency lesioning in the brain
    2009 (English)In: Journal of Biomedical Optics, ISSN 1083-3668, E-ISSN 1560-2281, Vol. 14, no 044040Article in journal (Refereed) Published
    Abstract [en]

    An electrode with adjacent optical fibers for measurements during navigation and radio frequency lesioning in the brain was modeled for Monte Carlo simulations of light transport in brain tissue. Relative reflected light intensity at 780 nm, I780, from this electrode and probes with identical fiber configuration were simulated using the intensity from native white matter as reference. Models were made of homogeneousnative and coagulated gray, thalamus, and white matter as well as blood. Dual layermodels, including models with a layer of cerebrospinal fluid between the fibers andthe brain tissue, were also made. Simulated I780 was 0.16 for gray matter, 0.67 forcoagulate gray matter, 0.36 for thalamus, 0.39 for coagulated thalamus, unity forwhite matter, 0.70 for coagulated white matter and 0.24 for blood. Thalamic matterhas also been found to reflect more light than gray matter and less than white matterin clinical studies. In conclusion the reflected light intensity can be used todifferentiate between gray and white matter during navigation. Furthermore,coagulation of light gray tissue, such as the thalamus, might be difficult to detectusing I780, but coagulation in darker gray tissue should result in a rapid increase of I780.

    Place, publisher, year, edition, pages
    SPIE - International Society for Optical Engineering, 2009
    Keywords
    Brain, Monte Carlo simulations, diffuse reflectance, navigation, radio-frequency lesioning
    National Category
    Bioengineering Equipment
    Identifiers
    urn:nbn:se:liu:diva-15930 (URN)10.1117/1.3210781 (DOI)000270540100046 ()19725751 (PubMedID)2-s2.0-73349106860 (Scopus ID)
    Note

    Original Publication: Johannes D. Johansson, Ingemar Fredriksson, Karin Wårdell and Ola Eriksson, Simulation of reflected light intensity changes during navigation and radio frequency lesioning in the brain, Journal of Biomedical Optics, (14), 044040, (2009). http://dx.doi.org/10.1117/1.3210781 Copyright 2009 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.

    Available from: 2008-12-16 Created: 2008-12-16 Last updated: 2017-12-14Bibliographically approved
  • 6.
    Johansson, Johannes
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Spectroscopic method for determination of the absorption coefficient in brain tissue2010In: Journal of Biomedical Optics, ISSN 1083-3668, E-ISSN 1560-2281, Vol. 15, no 5, p. 057005-1-057005-9Article in journal (Refereed)
    Abstract [en]

    I use MonteCarlo simulations and phantom measurements to characterize a probe withadjacent optical fibres for diffuse reflectance spectroscopy during stereotactic surgeryin the brain. Simulations and measurements have been fitted toa modified Beer–Lambert model for light transport in order tobe able to quantify chromophore content based on clinically measuredspectra in brain tissue. It was found that it isimportant to take the impact of the light absorption intoaccount when calculating the apparent optical path length, lp, forthe photons in order to get good estimates of theabsorption coefficient, µa. The optical path length was found tobe well fitted to the equation lp=a+b ln(Is)+c ln(µa)+d ln(Is)ln(µa), where Is isthe reflected light intensity for scattering alone (i.e., zero absorption).Although coefficients ad calculated in this study are specific tothe probe used here, the general form of the equationshould be applicable to similar probes.

  • 7.
    Johansson, Johannes
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Thermocoagulation in Deep Brain Structures: Modelling, simulation and experimental study of radio-frequency lesioning2006Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Radio-frequency (RF) lesioning is a method utilising high frequency currents for thermal coagulation of pathological tissue or signal pathways. The current is delivered from an electrode with a temperature sensor, permitting control of the current at a desired target temperature. In the brain RF-lesioning can e.g. be used for severe chronic pain and movement disorders such as Parkinson’s disease. This thesis focuses on modelling and simulation with the aim of gaining better understanding and predictability of the lesioning process in deep brain structures. The finite element method (FEM) together with experimental comparisons was used to study the effects of electrode dimensions, electrode target temperature, electric and thermal conductivity of the brain tissue, blood perfusion and cerebrospinal fluid (CSF) filled cysts. Equations for steady current, thermal transport and incompressible flow were used together with statistical factorial design and regression analysis for this purpose.

    Increased target temperature, electrode tip length and electrode diameter increased the simulated lesion size, which is in accordance with experimental results. The influence of blood perfusion, modelled as an increase in thermal conductivity in non-coagulated tissue, gave smaller simulated lesions with increasing blood perfusion as heat was more efficiently conducted from the rim of the lesion. If no consideration was taken to the coagulation the lesion became larger with increased thermal conductivity instead, as the increase in conducted heat was compensated for through an increased power output in order to maintain the target temperature. Simulated lesions corresponded well to experimental in-vivo lesions.

    The electric conductivity in a homogeneous surrounding had little impact on lesion development. However this was not valid for a heterogeneous surrounding. CSF-filled cysts have a much higher electric conductivity than brain tissue focussing the current to them if the electrode tip is in contact with both. Heating of CSF can also cause considerable convective flow and as a result a very efficient heat transfer. This affected simulated as well as experimental lesion sizes and shapes resulting in both very large lesions if sufficient power compared to the cysts size was supplied and very small lesions if the power was low, mitigating the heat over a large volume.

    In conclusion especially blood perfusion and CSF can greatly affect the lesioning process and appear to be important to consider when planning surgical procedures. Hopefully this thesis will help improve knowledge about and predictability of clinical lesioning.

    List of papers
    1. Radio-frequency lesioning in brain tissue with coagulation-dependent thermal conductivity: modelling, simulation and analysis of parameter influence and interaction
    Open this publication in new window or tab >>Radio-frequency lesioning in brain tissue with coagulation-dependent thermal conductivity: modelling, simulation and analysis of parameter influence and interaction
    Show others...
    2006 (English)In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 44, no 9, p. 757-766Article in journal (Refereed) Published
    Abstract [en]

    Radio-frequency brain lesioning is a method for reducing e.g. symptoms of movement disorders. A small electrode is used to thermally coagulate malfunctioning tissue. Influence on lesion size from thermal and electric conductivity of the tissue, microvascular perfusion and preset electrode temperature was investigated using a finite-element model. Perfusion was modelled as an increased thermal conductivity in non-coagulated tissue. The parameters were analysed using a 24-factorial design (n = 16) and quadratic regression analysis (n = 47). Increased thermal conductivity of the tissue increased lesion volume, while increased perfusion decreased it since coagulation creates a thermally insulating layer due to the cessation of blood perfusion. These effects were strengthened with increased preset temperature. The electric conductivity had negligible effect. Simulations were found realistic compared to in vivo experimental lesions.

    Place, publisher, year, edition, pages
    Heidleberg: Springer, 2006
    Keywords
    Electrosurgery, RF ablation, Brain, Blood perfusion, Finite-element method
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-15926 (URN)10.1007/s11517-006-0098-1 (DOI)000240378700003 ()16941099 (PubMedID)2-s2.0-33748485613 (Scopus ID)
    Note

    The original publication is available at www.springerlink.com: Johannes D Johansson, Ola Eriksson, Joakim Wren, Dan Loyd and Karin Wårdell, Radio-frequency lesioning in brain tissue with coagulation-dependent thermal conductivity: modelling, simulation and analysis of parameter influence and interaction, 2006, Medical and Biological Engineering and Computing, (44), 9, 757-766. http://dx.doi.org/10.1007/s11517-006-0098-1 Copyright: Springer Science Business Media http://www.springerlink.com/

    Available from: 2008-12-16 Created: 2008-12-16 Last updated: 2017-12-14Bibliographically approved
    2. Comparison between a detailed and a simplified finite element model of radio-frequency lesioning in the brain
    Open this publication in new window or tab >>Comparison between a detailed and a simplified finite element model of radio-frequency lesioning in the brain
    Show others...
    2004 (English)In: 26th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, San Fransisco, USA, 2004, Vol. 4, p. 2510-2513Conference paper, Published paper (Refereed)
    Abstract [en]

    A detailed and a simplified model of a lesioning electrode was made using the finite element method. 15 simulations of the lesioning procedure were performed for each model and the resulting lesion volumes were compared in order to investigate if the simplified model is adequate. The simplified model resulted in a very slight overestimation of the volume compared to the detailed model. It was thus concluded that the simplified model is adequate for simulations.

    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-13995 (URN)10.1109/IEMBS.2004.1403723 (DOI)
    Available from: 2006-09-25 Created: 2006-09-25 Last updated: 2018-10-08Bibliographically approved
    3. Simulations of radio-frequency lesions with varying brain electrode dimensions
    Open this publication in new window or tab >>Simulations of radio-frequency lesions with varying brain electrode dimensions
    Show others...
    2005 (English)In: 13th Nordic Baltic conference biomedical engineering and medical physics, Umeå, Sweden, 2005, Vol. 9, p. 62-63Conference paper, Published paper (Refereed)
    Abstract [en]

    Radio-frequency (RF) lesioning in the

    brain was simulated using the finite element method

    (FEM). Heating for 60 s with temperature control in

    order to keep the tip at 80 °C was simulated. Length,

    L, (2 – 4 mm) and diameter, D, (0.5 – 2.5 mm) of the

    electrode tip were varied and the resulting lesion

    volumes were used to calculate a regression model:

    Lesion Volume = – 13.1D + 15.7LD + 13.1D2 mm3.

    The results can be useful for electrode design and

    prediction of lesion size.

    Keywords
    Radio-frequency surgery, Brain, Lesion size, Electrode dimensions, Finite Element Method (FEM)
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-13996 (URN)
    Available from: 2006-09-25 Created: 2006-09-25 Last updated: 2017-02-21Bibliographically approved
    4. Impact of cysts during radio frequency (RF) lesioning in deep brain structures: a simulation and in-vitro study
    Open this publication in new window or tab >>Impact of cysts during radio frequency (RF) lesioning in deep brain structures: a simulation and in-vitro study
    2007 (English)In: Journal of Neural Engineering, ISSN 1741-2560, E-ISSN 1741-2552, Vol. 4, no 2, p. 87-95Article in journal (Refereed) Published
    Abstract [en]

    Radiofrequency lesioning of nuclei in the thalamus or the basal ganglia can be used to reduce symptoms caused by e.g. movement disorders such as Parkinson's disease. Enlarged cavities containing cerebrospinal fluid (CSF) are commonly present in the basal ganglia and tend to increase in size and number with age. Since the cavities have different electrical and thermal properties compared with brain tissue, it is likely that they can affect the lesioning process and thereby the treatment outcome. Computer simulations using the finite element method and in vitro experiments have been used to investigate the impact of cysts on lesions' size and shape. Simulations of the electric current and temperature distributions as well as convective movements have been conducted for various sizes, shapes and locations of the cysts as well as different target temperatures. Circulation of the CSF caused by the heating was found to spread heat effectively and the higher electric conductivity of the CSF increased heating of the cyst. These two effects were together able to greatly alter the resulting lesion size and shape when the cyst was in contact with the electrode tip. Similar results were obtained for the experiments.

    Place, publisher, year, edition, pages
    Institute of Physics Publishing (IOPP), 2007
    Keywords
    Electrosurgery, RF ablation, Brain, Blood perfusion, Finite-element method
    National Category
    Other Medical Engineering
    Identifiers
    urn:nbn:se:liu:diva-13997 (URN)10.1088/1741-2560/4/2/009 (DOI)000247947300015 ()17409483 (PubMedID)2-s2.0-34247183212 (Scopus ID)
    Note

    Original Publication: Johannes D. Johansson, Dan Loyd, Karin Wårdell and Joakim Wren, Impact of cysts during radio frequency (RF) lesioning in deep brain structures: a simulation and in-vitro study, 2006, Journal of Neural Ingeneering, (4), 2, 87-95. http://dx.doi.org/10.1088/1741-2560/4/2/009 Copyright: Institute of Physics Publishing http://www.iop.org/

    Available from: 2008-12-16 Created: 2008-12-16 Last updated: 2017-12-13Bibliographically approved
  • 8.
    Johansson, Johannes
    et al.
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
    Akbarian-Tefaghi, Ladan
    Unit of Functional Neurosurgery, Sobell Department of Motor Neuroscience, UCL Institute of Neurology, London, UK..
    Harith, Akram
    Unit of Functional Neurosurgery, Sobell Department of Motor Neuroscience, UCL Institute of Neurology, London, UK..
    Zrinzo, Ludvic
    Unit of Functional Neurosurgery, Sobell Department of Motor Neuroscience, UCL Institute of Neurology, London, UK..
    Limousin, Patricia
    Unit of Functional Neurosurgery, Sobell Department of Motor Neuroscience, UCL Institute of Neurology, London, UK..
    Joyce, Eileen
    Unit of Functional Neurosurgery, Sobell Department of Motor Neuroscience, UCL Institute of Neurology, London, UK..
    Hariz, Marwan
    Unit of Functional Neurosurgery, Sobell Department of Motor Neuroscience, UCL Institute of Neurology, London, UK..
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
    Foltynie, Tom
    Unit of Functional Neurosurgery, Sobell Department of Motor Neuroscience, UCL Institute of Neurology, London, UK..
    Estimation of effective target area in the globus pallidus during deep brain stimulation for Tourette syndrome.2017Conference paper (Refereed)
  • 9.
    Johansson, Johannes
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Blomstedt, P.
    Department of Neurosurgery University Hospital, Umeå, Sweden.
    Haj-Hosseini, Neda
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Bergenheim, A. T.
    Department of Neurosurgery University Hospital, Umeå, Sweden.
    Hariz, M. I.
    Department of Neurosurgery University Hospital, Umeå, Sweden.
    Eriksson, Ola
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Wårdell, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Combined electric impedance and optical diffuse reflectance measurements for navigation aid in deep brain surgery2008In: XVIII Congress of the European Society for Stereotactic and Functional Neurosurgery,2008, 2008Conference paper (Other academic)
  • 10.
    Johansson, Johannes
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Blomstedt, Patric
    Neurokirurgiska kliniken Norrlands universitetssjukhus.
    Hariz, Marwan
    Institute of Neurology University College, London, UK.
    Bergenheim, Tommy
    Neurokirurgiska kliniken Norrlands universitetssjukhus.
    Eriksson, Ola
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Wårdell, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Simultan jämförande mätning av elektrisk impedans och reflekterat ljus för guidning vid stereotakisk neurokirurgi2007In: Medicinteknikdagarna,2007, 2007Conference paper (Other academic)
  • 11.
    Johansson, Johannes D.
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Blomstedt, Patric
    Department of Neurosurgery, Norrland´s University Hospital, Umeå, Sweden.
    Haj-Hosseini, Neda
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Bergenheim, Tommy
    Department of Neurosurgery, Norrland´s University Hospital, Umeå, Sweden.
    Eriksson, Ola
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Combined diffuse light reflectance and electric impedance measurements for navigation aid in deep brain surgery2009In: Stereotactic and Functional Neurosurgery, ISSN 1011-6125, E-ISSN 1423-0372, Vol. 87, no 2, p. 105-113Article in journal (Refereed)
    Abstract [en]

    Aim: The aim of this study is to investigate reflected light intensity combined with impedance for navigation aid during stereotactic neurosurgery.

    Methods: During creation of 21 trajectories for stereotactic implantation of deep brain stimulation electrodes in the globus pallidus internus or subthalamus (zona incerta or subthalamic nucleus), impedance at 512 kHz and reflected light intensity at 780 nm were measured continuously and simultaneously with a radio frequency electrode containing optical fibres. The signals were compared with anatomy determined from pre- and postoperative MRI and CT. The measurements were performed within minutes and signal analysis was done post-operatively.

    Results: Reflected light intensity was low from cortex, lateral ventricle, caudate nucleus and putamen. It was intermediate from globus pallidus and thalamus while it was high from subcortical white matter, internal capsule and the subthalamus. The electric impedance was less consistent but generally low in the cortex, intermediate in subcortical white matter, the putamen, the globus pallidus and the thalamus and high in the internal capsule and the subthalamus.

    Conclusion: Reflected light intensity and electric impedance give complementary information about passed tissue and the combination seems promising for navigation aid during stereotactic neurosurgery.

  • 12.
    Johansson, Johannes D.
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Eriksson, Ola
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Wren, Joakim
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Loyd, Dan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Comparison between a detailed and a simplified finite element model of radio-frequency lesioning in the brain2004In: 26th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, San Fransisco, USA, 2004, Vol. 4, p. 2510-2513Conference paper (Refereed)
    Abstract [en]

    A detailed and a simplified model of a lesioning electrode was made using the finite element method. 15 simulations of the lesioning procedure were performed for each model and the resulting lesion volumes were compared in order to investigate if the simplified model is adequate. The simplified model resulted in a very slight overestimation of the volume compared to the detailed model. It was thus concluded that the simplified model is adequate for simulations.

  • 13.
    Johansson, Johannes D
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Eriksson, Ola
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Wren, Joakim
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Loyd, Dan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Radio-frequency lesioning in brain tissue with coagulation-dependent thermal conductivity: modelling, simulation and analysis of parameter influence and interaction2006In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 44, no 9, p. 757-766Article in journal (Refereed)
    Abstract [en]

    Radio-frequency brain lesioning is a method for reducing e.g. symptoms of movement disorders. A small electrode is used to thermally coagulate malfunctioning tissue. Influence on lesion size from thermal and electric conductivity of the tissue, microvascular perfusion and preset electrode temperature was investigated using a finite-element model. Perfusion was modelled as an increased thermal conductivity in non-coagulated tissue. The parameters were analysed using a 24-factorial design (n = 16) and quadratic regression analysis (n = 47). Increased thermal conductivity of the tissue increased lesion volume, while increased perfusion decreased it since coagulation creates a thermally insulating layer due to the cessation of blood perfusion. These effects were strengthened with increased preset temperature. The electric conductivity had negligible effect. Simulations were found realistic compared to in vivo experimental lesions.

  • 14.
    Johansson, Johannes D.
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Eriksson, Ola
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Wren, Joakim
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Loyd, Dan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Health Sciences.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Simulations of radio-frequency lesions with varying brain electrode dimensions2005In: 13th Nordic Baltic conference biomedical engineering and medical physics, Umeå, Sweden, 2005, Vol. 9, p. 62-63Conference paper (Refereed)
    Abstract [en]

    Radio-frequency (RF) lesioning in the

    brain was simulated using the finite element method

    (FEM). Heating for 60 s with temperature control in

    order to keep the tip at 80 °C was simulated. Length,

    L, (2 – 4 mm) and diameter, D, (0.5 – 2.5 mm) of the

    electrode tip were varied and the resulting lesion

    volumes were used to calculate a regression model:

    Lesion Volume = – 13.1D + 15.7LD + 13.1D2 mm3.

    The results can be useful for electrode design and

    prediction of lesion size.

  • 15.
    Johansson, Johannes D.
    et al.
    ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Sciences and Technology.
    Farzam, Parisa
    ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Sciences and Technology.
    Mireles, Miguel
    ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Sciences and Technology.
    Jiménez Valerio, Gabriela
    Bellvitge Biomedical Research Institute–IDIBELL.
    Martínez Lozano, Mar
    Bellvitge Biomedical Research Institute–IDIBELL.
    Casanovas, Oriol
    Bellvitge Biomedical Research Institute–IDIBELL.
    Durduran, Turgut
    ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Sciences and Technology.
    Optical investigation of antiangiogenic therapy in renal cell carcinoma2015Conference paper (Other academic)
    Abstract [en]

    Diffuse optical spectroscopy and diffuse correlation spectroscopy was used to monitor antiangiogenic therapy in renal cell carcinoma. The measurements allowed for hemodynamic characterization of the tumors and to monitor the initial antiangiogenic effect and relate it to final vessel density and tumor size.

  • 16.
    Johansson, Johannes D.
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Fredriksson, Ingemar
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Eriksson, Ola
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Simulation of reflected light intensity changes during navigation and radio frequency lesioning in the brain2009In: Journal of Biomedical Optics, ISSN 1083-3668, E-ISSN 1560-2281, Vol. 14, no 044040Article in journal (Refereed)
    Abstract [en]

    An electrode with adjacent optical fibers for measurements during navigation and radio frequency lesioning in the brain was modeled for Monte Carlo simulations of light transport in brain tissue. Relative reflected light intensity at 780 nm, I780, from this electrode and probes with identical fiber configuration were simulated using the intensity from native white matter as reference. Models were made of homogeneousnative and coagulated gray, thalamus, and white matter as well as blood. Dual layermodels, including models with a layer of cerebrospinal fluid between the fibers andthe brain tissue, were also made. Simulated I780 was 0.16 for gray matter, 0.67 forcoagulate gray matter, 0.36 for thalamus, 0.39 for coagulated thalamus, unity forwhite matter, 0.70 for coagulated white matter and 0.24 for blood. Thalamic matterhas also been found to reflect more light than gray matter and less than white matterin clinical studies. In conclusion the reflected light intensity can be used todifferentiate between gray and white matter during navigation. Furthermore,coagulation of light gray tissue, such as the thalamus, might be difficult to detectusing I780, but coagulation in darker gray tissue should result in a rapid increase of I780.

  • 17.
    Johansson, Johannes D.
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Loyd, Dan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Wren, Joakim
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Impact of cysts during radio frequency (RF) lesioning in deep brain structures: a simulation and in-vitro study2007In: Journal of Neural Engineering, ISSN 1741-2560, E-ISSN 1741-2552, Vol. 4, no 2, p. 87-95Article in journal (Refereed)
    Abstract [en]

    Radiofrequency lesioning of nuclei in the thalamus or the basal ganglia can be used to reduce symptoms caused by e.g. movement disorders such as Parkinson's disease. Enlarged cavities containing cerebrospinal fluid (CSF) are commonly present in the basal ganglia and tend to increase in size and number with age. Since the cavities have different electrical and thermal properties compared with brain tissue, it is likely that they can affect the lesioning process and thereby the treatment outcome. Computer simulations using the finite element method and in vitro experiments have been used to investigate the impact of cysts on lesions' size and shape. Simulations of the electric current and temperature distributions as well as convective movements have been conducted for various sizes, shapes and locations of the cysts as well as different target temperatures. Circulation of the CSF caused by the heating was found to spread heat effectively and the higher electric conductivity of the CSF increased heating of the cyst. These two effects were together able to greatly alter the resulting lesion size and shape when the cyst was in contact with the electrode tip. Similar results were obtained for the experiments.

  • 18.
    Johansson, Johannes D.
    et al.
    ICFO -The Institute of Photonic Sciences, Barcelona Institute of Science and Technology, Barcelona, Spain.
    Mireles, Miguel
    ICFO -The Institute of Photonic Sciences, Barcelona Institute of Science and Technology, Barcelona, Spain.
    Farzam, Parisa
    ICFO -The Institute of Photonic Sciences, Barcelona Institute of Science and Technology, Barcelona, Spain.
    Durduran, Turgut
    ICFO -The Institute of Photonic Sciences, Barcelona Institute of Science and Technology, Barcelona, Spain.
    Practical height correction for diffuse optical spectroscopy to account for curved tissue surfaces 2014In: Proceedings Biomedical optics 26-30 April 2014, Miami, Florida, United States, Optical Society of America, 2014Conference paper (Other academic)
    Abstract [en]

    Non-contact broadband diffuse optical spectroscopy that is meant for longitudinal study of superficial tumor models suffers from systematic errors due to tissue surface. We propose a practical height correction algorithm to minimize these errors.

  • 19.
    Johansson, Johannes D
    et al.
    ICFO - Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology.
    Mireles, Miguel
    ICFO - Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology.
    Morales-Dalmau, Jordi
    ICFO - Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology.
    Farzam, Parisa
    ICFO - Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology.
    Martínez-Lozano, Mar
    Program Against Cancer Therapeutic Resistance (ProCURE), Catalan Institute of Oncology, Bellvitge Biomedical Research Institute –IDIBELL.
    Casanovas, Oriol
    Program Against Cancer Therapeutic Resistance (ProCURE), Catalan Institute of Oncology, Bellvitge Biomedical Research Institute –IDIBELL.
    Durduran, Turgut
    ICFO - Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology.
    Scanning, non-contact, hybrid broadband diffuse optical spectroscopy and diffuse correlation spectroscopy system.2016In: Biomedical Optics Express, ISSN 2156-7085, E-ISSN 2156-7085, Vol. 7, no 2, p. 481-498Article in journal (Refereed)
    Abstract [en]

    A scanning system for small animal imaging using non-contact, hybrid broadband diffuse optical spectroscopy (ncDOS) and diffuse correlation spectroscopy (ncDCS) is presented. The ncDOS uses a two-dimensional spectrophotometer retrieving broadband (610-900 nm) spectral information from up to fifty-seven source-detector distances between 2 and 5 mm. The ncDCS data is simultaneously acquired from four source-detector pairs. The sample is scanned in two dimensions while tracking variations in height. The system has been validated with liquid phantoms, demonstrated in vivo on a human fingertip during an arm cuff occlusion and on a group of mice with xenoimplanted renal cell carcinoma.

  • 20.
    Johansson, Johannes D.
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Health Sciences.
    Zerbinati, Alice
    Politecnico di Torino, Turin, Italy.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Health Sciences.
    Diffuse Reflectance Spectroscopy During Experimental Radio Frequency Ablation2008In: 14th Nordic-Baltic Conference on Biomedical Engineering and Medical Physics: NBC 2008 16–20 June 2008 Riga, Latvia / [ed] Alexei Katashev, Yuri Dekhtyar, Janis Spigulis, Heidelberg: Springer Berlin/Heidelberg, 2008, p. 371-374Chapter in book (Refereed)
    Abstract [en]

    The aim of the study was to investigate the spectral changes during heating and to estimate threshold temperatures for initiation of the thermal coagulation. A brain electrode with optical fibers was used to generate lesions in ex-vivo porcine white and gray matter as well as in fat and meat from pork chop. Radio frequency ablation (60 s, 48–90 °C, steps of 2-10 °C) was performed while simultaneous spectroscopy measurements were made in the range 490–900 nm.

    The optical signal recorded from porcine gray and white brain matter was unstable with the reflected light intensity fluctuating a lot. Nevertheless an abrupt increase in light intensity during coagulation in gray matter was found at 48 ± 6 °C (n = 21), probably indicating onset of coagulation. The reflected light intensity from white matter showed no consistent behavior during coagulation.

    The results for pork chop meat and fat were considerably more consistent. The reflected light intensity from pork chop meat stayed stable up to a mean temperature of 42.5 ± 3.5 °C (n = 11). Above this temperature it abruptly increased for all wavelengths. The reflected light intensity from pork chop fat dropped over all wavelengths immediately as the temperature increased and remained low as the fat cooled (n = 8).

    In conclusion diffuse reflectance spectroscopy appears to be suitable to detect onset of coagulation in muscle tissue and gray matter. The estimated initiation temperature of coagulation varied and was dependent on tissue type.

  • 21.
    Johansson, Johannes
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Eriksson, O.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    A system for optical guidance during stereotactic neurosurgery2010Conference paper (Refereed)
  • 22.
    Johansson, Johannes
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Eriksson, O.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Models for computer simulations of RF lesions in brain tissue2002Conference paper (Refereed)
  • 23.
    Johansson, Johannes
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Eriksson, Ola
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Wren, Joakim
    Linköping University, Department of Mechanical Engineering.
    Loyd, Dan
    Linköping University, Department of Mechanical Engineering.
    Wårdell, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    FEM-modell för termisk koagulering i hjärnvävnad2003In: Svenska lakaresallskapets riksstamma,2003, 2003, p. 242-242Conference paper (Other academic)
  • 24.
    Johansson, Johannes
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Fredriksson, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Eriksson, Ola
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Wårdell, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Simulering av ljusreflektion i hjärnan under navigation och radiofrekvensablation2008In: Medicinteknikdagarna 2008,2008, 2008, p. 70-70Conference paper (Other academic)
  • 25.
    Johansson, Johannes
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Fredriksson, Ingemar
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Eriksson, Ola
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Monte Carlo simulations of reflected light intensity for navigation in the brain2009Conference paper (Other academic)
  • 26.
    Johansson, Johannes
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Loyd, Dan
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Wårdell, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Wren, Joakim
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    The influence of CSF-filled cavities on radio-frequency lesions - a simulation study2006In: Congress of the European Society for Stereotactic and Functional Neurosurgery,2006, New York: Springer , 2006Conference paper (Other academic)
  • 27.
    Johansson, Johannes
    et al.
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
    Portaluppi, Davide
    Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milano, Italien.
    Buttafava, Mauro
    Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milano, Italien.
    Villa, Federica
    Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milano, Italien.
    Development of a hybrid laser Doppler flowmetry and diffuse correlation spectroscopy system2018Conference paper (Refereed)
  • 28.
    Johansson, Johannes
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Wren, Joakim
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Eriksson, O.
    Loyd, Dan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Teoretisk och experimentell undersökning av värmekoagulation med radiofrekvent ström i hjärna2005Conference paper (Refereed)
  • 29.
    Johansson, Johannes
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Wren, Joakim
    Linköping University, Department of Mechanical Engineering.
    Eriksson, Ola
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Loyd, Dan
    Linköping University, Department of Mechanical Engineering.
    Wårdell, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Investigation of brain RF-lesion size by finite element simulations2004In: European Society for Stereotactic and Functional Neurosurgery ESSFN,2004, Wien: Springer Verlag , 2004, p. 932-932Conference paper (Other academic)
  • 30.
    Johansson, Johannes
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Wren, Joakim
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Loyd, Dan
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Eriksson, Ola
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Wårdell, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Konvektiva flöden och deras termiska inverkan vid Radiofrekvenslesionering i hjärna2006In: Medicinteknikdagarna 2006,2006, 2006Conference paper (Other academic)
    Abstract [en]

       

  • 31.
    Johansson, Johannes
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Intracerebral quantitative chromophore estimation from reflectance spectra captured during deep brain stimulation implantation2013In: Journal of Biophotonics, ISSN 1864-063X, E-ISSN 1864-0648, Vol. 6, no 5, p. 435-445Article in journal (Refereed)
    Abstract [en]

    Quantification of blood fraction (fblood), blood oxygenation (S), melanin, lipofuscin and oxidised and reduced Cytochrome aa 3 and c was done from diffuse reflectance spectra captured in cortex, white matter, globus pallidus internus (GPi) and subthalamus during stereotactic implantations of 29 deep brain stimulation (DBS) electrodes with the aim of investigating whether the chromophores can give physiological information about the targets for DBS. Double-sided Mann-Whitney U -tests showed more lipofuscin in GPi compared to white matter and subthalamus (p < 0.05). Compared to the other structures, fbloodwas significantly higher in cortex (p < 0.05) and S lower in GPi (p < 0.05). Median values and range for fblood were 1.0 [0.2–6.0]% in the cortex, 0.3 [0.1–8.2]% in white matter, 0.2 [0.1–0.8]% in the GPi and 0.2 [0.1–11.7]% in the subthalamus. Corresponding values for S was 20 [0–81]% in the cortex, 29 [0–78]% in white matter, 0 [0–0]% in the GPi and 0 [0–92]% in the subthalamus. In conclusion, the measurements indicate very low oxygenation and blood volume for DBS patients, especially in the GPi. It would be of great interest to investigate whether this is due to the disease, the normal situation or an artefact of doing invasive measurements.

  • 32.
    Lindner, Claus
    et al.
    ICFO - Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology.
    Mora, Mireia
    Department of Endocrinology and Nutrition, Hospital Clínic, Barcelona, Spain.
    Farzam, Parisa
    ICFO - Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology.
    Squarcia, Mattia
    Department of Endocrinology and Nutrition, Hospital Clínic, Barcelona, Spain.
    Johansson, Johannes
    ICFO - Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology.
    Weigel, Udo M
    ICFO - Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology.
    Halperin, Irene
    Department of Endocrinology and Nutrition, Hospital Clínic, Barcelona, Spain.
    Hanzu, Felicia A
    Department of Endocrinology and Nutrition, Hospital Clínic, Barcelona, Spain.
    Durduran, Turgut
    ICFO - Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology.
    Diffuse Optical Characterization of the Healthy Human Thyroid Tissue and Two Pathological Case Studies.2016In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 11, no 1Article in journal (Refereed)
    Abstract [en]

    The in vivo optical and hemodynamic properties of the healthy (n = 22) and pathological (n = 2) human thyroid tissue were measured non-invasively using a custom time-resolved spectroscopy (TRS) and diffuse correlation spectroscopy (DCS) system. Medical ultrasound was used to guide the placement of the hand-held hybrid optical probe. TRS measured the absorption and reduced scattering coefficients (μa, μs') at three wavelengths (690, 785 and 830 nm) to derive total hemoglobin concentration (THC) and oxygen saturation (StO2). DCS measured the microvascular blood flow index (BFI). Their dependencies on physiological and clinical parameters and positions along the thyroid were investigated and compared to the surrounding sternocleidomastoid muscle. The THC in the thyroid ranged from 131.9 μM to 144.8 μM, showing a 25-44% increase compared to the surrounding sternocleidomastoid muscle tissue. The blood flow was significantly higher in the thyroid (BFIthyroid = 16.0 × 10-9 cm2/s) compared to the muscle (BFImuscle = 7.8 × 10-9 cm2/s), while StO2 showed a small (StO2, muscle = 63.8% to StO2, thyroid = 68.4%), yet significant difference. Two case studies with thyroid nodules underwent the same measurement protocol prior to thyroidectomy. Their THC and BFI reached values around 226.5 μM and 62.8 × 10-9 cm2/s respectively showing a clear contrast to the nodule-free thyroid tissue as well as the general population. The initial characterization of the healthy and pathologic human thyroid tissue lays the ground work for the future investigation on the use of diffuse optics in thyroid cancer screening.

  • 33.
    Lindner, Claus
    et al.
    ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Sciences and Technology.
    Mora Porta, Mireia
    Department of Endocrinology and Nutrition, Hospital Clínic, Barcelona.
    Farzam, Parisa
    ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Sciences and Technology.
    Squarcia, Mattia
    Department of Endocrinology and Nutrition, Hospital Clínic, Barcelona.
    Johansson, Johannes D.
    ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Sciences and Technology.
    Weigel, Udo
    ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Sciences and Technology.
    Halperin, Irene
    Department of Endocrinology and Nutrition, Hospital Clínic, Barcelona.
    Hanzu, Felicia
    Department of Endocrinology and Nutrition, Hospital Clínic, Barcelona.
    Durduran, Turgut
    ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Sciences and Technology.
    Diffuse optical characterization of the human thyroid2016Conference paper (Refereed)
    Abstract [en]

    The human thyroid was measured by ultrasound-guided near-infrared time-resolved spectroscopy and diffuse correlation spectroscopy characterizing the healthy thyroid and nodules allowing us to envision applications in thyroid cancer screening.

  • 34.
    Mireles, Miguel
    et al.
    ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Sciences and Technology.
    Johansson, Johannes D.
    ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Sciences and Technology.
    Farzam, Parisa
    ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Sciences and Technology.
    Martínez Lozano, Mar
    Bellvitge Biomedical Research Institute–IDIBELL.
    Casanovas, Oriol
    Bellvitge Biomedical Research Institute–IDIBELL.
    Durduran, Turgut
    ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Sciences and Technology.
    Morales, Jordí
    ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Sciences and Technology.
    A non-contact, small animal scanner based on diffuse optical spectroscopy and diffuse correlation spectroscopy2016Conference paper (Refereed)
    Abstract [en]

    A scanning system that combines broadband diffuse optical spectroscopy and diffuse correlation spectroscopy for non-contact, large field-of-view imaging of small animal models and humans is presented and demonstrated in vivo.

  • 35.
    Morales, Jordí
    et al.
    ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Sciences and Technology.
    Mireles, Miguel
    ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Sciences and Technology.
    Johansson, Johannes D.
    ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Sciences and Technology.
    Martínez Lozano, Mar
    Bellvitge Biomedical Research Institute–IDIBELL.
    Vilches, Clara
    ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Sciences and Technology.
    Casanovas, Oriol
    Bellvitge Biomedical Research Institute–IDIBELL.
    Quidant, Romain
    ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Sciences and Technology.
    Durduran, Turgut
    ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Sciences and Technology.
    Simultaneous, non-invasive measurement of local tissue hemodynamics, oxygen metabolism and gold nanorod concentration in vivo2016Conference paper (Refereed)
    Abstract [en]

    A hybrid broadband diffuse optical and diffuse correlation spectroscopy system is used to measure local tissue hemodynamics, oxygen metabolism and gold nanorod concentration. The objective is to provide real-time feed-back for photothermal therapy.

  • 36.
    Rejmstad, Peter
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering.
    Johansson, Johannes D.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering.
    Haj-Hosseini, Neda
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering.
    A method for monitoring of oxygen saturation changes in brain tissue using diffuse reflectance spectroscopy2017In: Journal of Biophotonics, ISSN 1864-063X, E-ISSN 1864-0648, Vol. 10, no 3, p. 446-455Article in journal (Refereed)
    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.

  • 37.
    Wårdell, Karin
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Johansson, Johannes
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    A System for Optical Guidance during Stereotactic Neurosurgery (oral)2010Conference paper (Refereed)
  • 38.
    Wårdell, Karin
    et al.
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
    Johansson, Johannes
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
    Alonso, Fabiola
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
    Deep brain stimulation: software for patient-specific electric field simulations2017Conference paper (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.

  • 39.
    Wårdell, Karin
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Johansson, Johannes
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Richter, Johan
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology. Östergötlands Läns Landsting, Anaesthetics, Operations and Specialty Surgery Center, Department of Neurosurgery.
    Blomstedt, Patric
    Dept of Neurosurgery, Umeå University Hospital, Sweden.
    Optical measurements for guidance during deep brain stimulation surgery2009In: World Congress on Medical Physics and Biomedical Engineering / [ed] Olaf Dössel and Wolfgang C. Schlegel, Berlin/Heidelberg: Springer , 2009, p. 516-517Conference paper (Refereed)
    Abstract [en]

    Deep brain stimulation (DBS) is an established treatment for Parkinson’s disease and related movement disorders. The success of DBS is highly dependent on electrode location, electrical parameter settings and the surgical procedure. In this paper an overview of the current status of optical measurements for intracerebral guidance performed during DBS implantation is presented. Laser Doppler perfusion monitoring and/or reflection spectroscopy measurements have been done in relation to more than 70 DBS lead implantations to wards targets in the deep brain structures. The techniques have also been compared with impedance monitoring, and simulation of the measurement depth has been done with Monte Carlo technique. These studies show that grey-white matter boundaries can be determined with a resolution higher than for both impedance measurements and magnetic resonance imaging.

  • 40.
    Åström, Mattias
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Johansson, Johannes
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Hariz, Marwan
    Institute of Neurology London.
    Eriksson, Ola
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Wårdell, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    The effect of cystic cavities on deep brain stimulation in the basal ganglia: A simulation-based study2006In: Journal of Neural Engineering, ISSN 1741-2560, E-ISSN 1741-2552, Vol. 3, no 2, p. 132-138Article in journal (Refereed)
    Abstract [en]

    Although the therapeutic effect of deep brain stimulation (DBS) is well recognized, a fundamental understanding of the mechanisms responsible is still not known. In this study finite element method (FEM) modelling and simulation was used in order to study relative changes of the electrical field extension surrounding a monopolar DBS electrode positioned in grey matter. Due to the frequently appearing cystic cavities in the DBS-target globus pallidus internus, a nucleus of grey matter with and without a cerebrospinal fluid filled cystic cavity was modelled. The position, size and shape of the cyst were altered in relation to the electrode. The simulations demonstrated an electrical field around the active element with decreasing values in the radial direction. A stepwise change was present at the edge between grey and white matters. The cyst increased the radial extension and changed the shape of the electrical field substantially. The position, size and shape of the cyst were the main influencing factors. We suggest that cystic cavities in the DBS-target may result in closely related unexpected structures or neural fibre bundles being stimulated and could be one of the reasons for suboptimal clinical effects or stimulation-induced side effects. © 2006 IOP Publishing Ltd.

  • 41.
    Åström, Mattias
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Johansson, Johannes
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Wårdell, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Modeling and simulation of electric fields generated by brain stimulation electrodes: the effect of cystic cavities in the basal ganglia2005In: Proceedings from the International IEEE EMBS Conference on Neural Engineering, IEEE , 2005, p. 198-201Conference paper (Refereed)
    Abstract [en]

    Deep brain stimulation (DBS) is an effective method for managing movement disorders. A small electrode is implanted in the basal ganglia and an electric potential is applied to one or more active elements of the electrode in order to simulate the neurons in the surrounding tissue. The fundamental understanding of the mechanisms responsible for the therapeutic DBS effects is unknown. A method to increase the knowledge is to use computer simulations. In this study the finite element method has been used for investigation of relative changes of the electrical field extension surrounding a monopolar DBS-electrode positioned in gray matter. Due to the frequently appearing cystic cavities in globus pallidus and putamen a nucleus of gray matter with and without a cerebrospinal fluid filled cystic cavity was modeled. The simulations demonstrated an electrical field around the active element with decreasing values in the radial direction. A stepwise change was present at the edge between gray and white matter. The cyst increased the radial extension and changed the shape of the field. This may result in closely related unexpected structures being stimulated and could be one of the reasons of reported postoperative complications.

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