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Combined diffuse light reflectance and electric impedance measurements for navigation aid in deep brain surgery
Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology. (MINT)
Department of Neurosurgery, Norrland´s University Hospital, Umeå, Sweden.
Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology. (MINT)ORCID iD: 0000-0002-0555-8877
Department of Neurosurgery, Norrland´s University Hospital, Umeå, Sweden.
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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.

Place, publisher, year, edition, pages
2009. Vol. 87, no 2, 105-113 p.
Keyword [en]
Stereotactic surgery, navigation, electric impedance, light reflectance
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-15929DOI: 10.1159/000202977OAI: oai:DiVA.org:liu-15929DiVA: diva2:128390
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
In thesis
1. Impact of Tissue Characteristics on Radio-Frequency Lesioning and Navigation in the Brain: Simulation, experimental and clinical studies
Open this publication in new window or tab >>Impact of Tissue Characteristics on Radio-Frequency Lesioning and Navigation in the Brain: Simulation, experimental and clinical studies
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
Brain, Radio frequency ablation, Finite element method, Monte Carlo simulation, light reflectance
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:liu:diva-15749 (URN)978-91-7393-723-8 (ISBN)
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

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Johansson, Johannes D.Haj-Hosseini, NedaEriksson, OlaWårdell, Karin

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