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Impact of Tissue Characteristics on Radio-Frequency Lesioning and Navigation in the Brain: Simulation, experimental and clinical studies
Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. (MINT)
2009 (English)Doctoral 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.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press , 2009. , 74 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1230
Keyword [en]
Brain, Radio frequency ablation, Finite element method, Monte Carlo simulation, light reflectance
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
URN: urn:nbn:se:liu:diva-15749ISBN: 978-91-7393-723-8 (print)OAI: oai:DiVA.org:liu-15749DiVA: diva2:128393
Public defence
2009-01-16, Linden, ingång 65, Campus US, Hälsouniversitetet, Linköpings universitet, Linköping, 09:15 (Swedish)
Opponent
Supervisors
Available from: 2008-12-17 Created: 2008-12-02 Last updated: 2017-02-10Bibliographically approved
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
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2006 (English)In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 44, no 9, 757-766 p.Article 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
Keyword
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: 2017-02-21Bibliographically 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, 87-95 p.Article 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
Keyword
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: 2017-02-16Bibliographically 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, 371-374 p.Chapter 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
Keyword
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
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2009 (English)In: Stereotactic and Functional Neurosurgery, ISSN 1011-6125, E-ISSN 1423-0372, Vol. 87, no 2, 105-113 p.Article 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.

Keyword
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: 2017-02-10Bibliographically 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
Keyword
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: 2017-02-10Bibliographically approved

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