liu.seSearch for publications in DiVA
Change search
ReferencesLink to record
Permanent link

Direct link
Diffuse Reflectance Spectroscopy During Experimental Radio Frequency Ablation
Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Health Sciences.
Politecnico di Torino, Turin, Italy.
Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Health Sciences.
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. 371-374 p.
, IFMBE Proceedings, ISSN 1680-0737 ; 20
Keyword [en]
Radio frequency ablation, diffuse reflectance spectroscopy, brain, muscle, fat
National Category
Medical and Health Sciences
URN: urn:nbn:se:liu:diva-15927DOI: 10.1007/978-3-540-69367-3_99ISBN: 978-3-540-69366-6 (print)ISBN: 978-3-540-69367-3 (online)OAI: diva2:128387
Available from: 2008-12-16 Created: 2008-12-16 Last updated: 2014-05-21Bibliographically 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.
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1230
Brain, Radio frequency ablation, Finite element method, Monte Carlo simulation, light reflectance
National Category
Radiology, Nuclear Medicine and Medical Imaging
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)
Available from: 2008-12-17 Created: 2008-12-02 Last updated: 2009-05-04Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textLink to the Ph.D. Thesisfind book at a swedish library/hitta boken i ett svenskt bibliotek

Search in DiVA

By author/editor
Johansson, Johannes D.Wårdell, Karin
By organisation
Biomedical InstrumentationFaculty of Health Sciences
Medical and Health Sciences

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 592 hits
ReferencesLink to record
Permanent link

Direct link