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Characterisation and modelling of radio-frequency lesioning in functional neurosurgery
Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
2001 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis focuses on the characterisation and modelling of the radio frequency (RF) lesioning with emphasis on size estimation in functional neurosurgery. A computer-assisted video system has been set up for standardised test and documentation of protein clots generated by RF-lesioning electrodes in an albumin solution. A standardised test is essential in comparing assessed results of the size and shape of protein clots generated using different parameters. This is beneficial to both the manufacturer oflesioning electrodes as well as the surgeon.

In an animal study, performed analogously to thalamotomy in man, the correlation in size between in vitro protein clots and in vivo lesions has been investigated. The result shows a high correlation between protein clots and lesions observed on MR images; and lesions observed on MR images and corresponding coagulated tissue in histological sectionings. This actualises the value of presurgical electrode tests to validate the electrode function and lesion size in vitro.

A finite element model has been set-up in order to facilitate studies of the growth and the temperature distribution during the lesioning process. Of the utmost importance is the finding of a difference in temperature between maximum temperature, located outside the electrode, compared to the intra-electrode (thermocouple) temperature.

A method for real time monitoring of lesion growth and estimation of lesion size utilising static and/or Doppler broadened laser light is proposed. Implemented in a surgical-assist system, this could give valuable guidance to the surgeon as to whether the desired lesion size is obtained or not and keep the destruction precise, but to a minimum.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet , 2001. , 70 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 693
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-29440Local ID: 14786ISBN: 91-7373-033-5 (print)OAI: oai:DiVA.org:liu-29440DiVA: diva2:250255
Public defence
2001-06-01, Elsa Brändströmssalen, Universitetssjukhuset, Linköping, 09:15 (Swedish)
Opponent
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2013-02-26
List of papers
1. In vitro evaluation of brain lesioning electrodes (Leksell) using a computer-assisted video system
Open this publication in new window or tab >>In vitro evaluation of brain lesioning electrodes (Leksell) using a computer-assisted video system
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1999 (English)In: Neurological Research, ISSN 0161-6412, E-ISSN 1743-1328, Vol. 21, no 1, 89-95 p.Article in journal (Refereed) Published
Abstract [en]

Radiofrequency (RF) generated thermal brain lesions are widely used in functional neurosurgery. The size, shape and development of the lesions depends on system parameter settings and the electrode configuration. Difficulties in studying the effect of these factors in vivo stimulated us to develop an in vitro system for standardized comparison between different electrodes and physical parameters. A computer-assisted video system was set-up allowing continuous video recording of RF-generated coagulations in either a standard albumin solution or in the fresh white of a hen's egg as transparent test substrates. Ten lesions were made with each test electrode (two bipolar and three monopolar) in each of the two substrates at 70 degrees, 80 degrees and 90 degrees C (t = 60 sec). Due to the better homogeneity the lesions in the albumin solution were much more regular and reproducible. This made it possible to calculate the size (width 2.2 +/- 0.1 to 5.3 +/- 0.1 mm and length 3.0 +/- 0.1 to 8.7 +/- 0.3 mm) as well as the volume (8.5 +/- 1.4 mm3 to 133.5 +/- 26.8 mm3). It is concluded that this in vitro system offers a reproducible way to study and document the effect of different electrode configurations and RF-generator settings on the formation of a heat lesion. Even if the results are not directly applicable to the living human brain they give an estimate of the form and size of a coagulation lesion and can be of value for standardized comparisons between different electrodes.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-30203 (URN)10048063 (PubMedID)15697 (Local ID)15697 (Archive number)15697 (OAI)
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2017-12-13
2. In-vitro size estimation of protein clots generated by brain electrodes
Open this publication in new window or tab >>In-vitro size estimation of protein clots generated by brain electrodes
1998 (English)In: Proceedings of the 20th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 1998 / [ed] H. K. Chang, Y. T. Zhang, Hong Kong: IEEE , 1998, 1783- p.Conference paper, Published paper (Refereed)
Abstract [en]

A method for in-vitro size estimation of protein clots generated by brain electrodes is presented. Radiofrequency generated thermal brain lesions are widely used in functional neurosurgery and in-vitro tests are used to confirm the electrodes' ability to generate lesions. To be able to estimate the size of protein clots generated in-vitro by brain electrodes, a computer-assisted video system was set up. The size estimation is carried out by software using two captured images of the protein clot. The “true” length and width (9.5 mm) of a sphere as measured with a slide-caliper differed at the most 0.5 mm (5%) and 0.3 mm (3%) respectively, all random errors fall within 2s.d

Place, publisher, year, edition, pages
Hong Kong: IEEE, 1998
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-31111 (URN)10.1109/IEMBS.1998.746933 (DOI)16842 (Local ID)16842 (Archive number)16842 (OAI)
Conference
The 20th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, October 29 - November 1 1998, Hong Kong SAR, China
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2016-05-04
3. Experimental radiofrequency brain lesions: a volumetric study
Open this publication in new window or tab >>Experimental radiofrequency brain lesions: a volumetric study
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2002 (English)In: Neurosurgery, ISSN 0148-396X, E-ISSN 1524-4040, Vol. 51, no 3, 781-788 p.Article in journal (Refereed) Published
Abstract [en]

OBJECTIVE : This study describes the production, under strictly standardized and controlled conditions, of radiofrequency lesions with identical neurogenerator settings: in vitro in two different albumin solutions (nongelatinous and gelatinous) and in vivo in the thalamus of the pig.

METHODS : The radiofrequency lesions were investigated in vitro by the use of a specially designed video system and in vivo by magnetic resonance imaging. Moreover, the size of the in vivo lesions was estimated with the use of histological sectioning. The statistical analysis included the calculation of a correlation coefficient for the length, width, and volume for each lesion estimation.

RESULTS : A high correlation (R = 0.96, P < 0.005; n = 14) was found between clot sizes in the two albumin solutions. Albumin clots generated in gelatinous albumin showed systematically larger volumes. In the pig, two concentric zones were seen in all magnetic resonance images and all histological preparations. The width correlation of the completely coagulated brain tissue (inner zones) was R = 0.94, P < 0.005, and n = 7. The corresponding correlation between magnetic resonance images and gelatinous albumin was R = 0.93, P < 0.005, and n = 7. As a rule, the in vitro clots were smaller than the outer zone but larger than the inner zone of the magnetic resonance imaging-recorded lesions for all of the electrode and temperature combinations tested. In vivo lesions generated with the same electrode and parameter settings showed high reproducibility.

CONCLUSION : The value of presurgical electrode tests to validate the electrode function and lesion size in vitro has become evident in this study, which shows a high correlation between the in vitro albumin clots and the in vivo lesions observed on magnetic resonance images.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-29944 (URN)10.1097/00006123-200209000-00030 (DOI)15370 (Local ID)15370 (Archive number)15370 (OAI)
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2017-12-13
4. A comparison between in vitro studies of protein lesions generated by brain electrodes and finite element model simulations
Open this publication in new window or tab >>A comparison between in vitro studies of protein lesions generated by brain electrodes and finite element model simulations
1999 (English)In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 37, no 6, 737-741 p.Article in journal (Refereed) Published
Abstract [en]

The aim of this study was to develop a finite element model for simulation of the thermal characteristics of brain electrodes and to compare its performances with an in vitro experimental albumin model. Ten lesions were created in albumin using a monopolar electrode connected to a Leksell Neuro Generator and a computer-assisted video system was used to determine the size of the generated lesions. A finite element model was set up of the in vitro experiments using the same thermal properties. With a very simple heat source applied to the finite element model in the proximity of the upper part of the tip, a good agreement (no deviations in width and distance from tip but a deviation in length of −1.6 mm) with the in vitro experiments (width 4.6±0.1 mm and length 7.4±0.1 mm) was achieved when comparing the outline of the lesion. In addition, a gelatinous albumin-model was set up and compared to computer simulations resulting in deviations in width of −0.4 mm, length of −2.2 mm and distance from the tip of −0.1 mm. Hence, the utilisation of finite element model simulations may be a useful complement to in-vitro experiments.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-30204 (URN)10.1007/BF02513376 (DOI)15698 (Local ID)15698 (Archive number)15698 (OAI)
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2017-12-13
5. Analysis of temperature measurement for monitoring radio-frequency brain lesioning
Open this publication in new window or tab >>Analysis of temperature measurement for monitoring radio-frequency brain lesioning
2001 (English)In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 39, no 2, 255-262 p.Article in journal (Refereed) Published
Abstract [en]

During ablative neurosurgery of movement disorders, for instance therapy of Parkinson's disease, temperature monitoring is crucial. This study aims at a quantitative comparison of measurement deviations between the maximum temperature located outside the lesioning electrode and two possible thermocouple locations inside the electrode. In order to obtain the detailed temperature field necessary for the analysis, four finite element models associated with different surroundings and with different power supplies are studied. The results from the simulations show that both the power level and the power density as well as the surrounding medium affect the temperature measurement and the temperature field in general. Since the maximum temperature is located outside the electrode there will always be a deviation in time and level between the measured and the maximum temperature. The deviation is usually 2–7 s and 3–12°C, depending on, for example, the thermocouple location and surrounding medium. Therefore, not only the measured temperature but also the relation between measured and maximum temperature must be accounted for during therapy and device design.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-29926 (URN)10.1007/BF02344810 (DOI)15351 (Local ID)15351 (Archive number)15351 (OAI)
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2017-12-13
6. Optical changes as a marker for lesion size estimation during radio frequency ablation: a model study
Open this publication in new window or tab >>Optical changes as a marker for lesion size estimation during radio frequency ablation: a model study
2001 (English)In: SPIE Proceedings | Volume 4254 | Guidance, Surgical-Assist and Treatment Systems / [ed] Warren S. Grundfest; David A. Benaron; Tuan Vo-Dinh, 2001, Vol. 4254, 164-171 p.Conference paper, Published paper (Other academic)
Abstract [en]

Stereotactic radiofrequency (RF)-lesioning in the central part of the brain is performed on patients that, for instance, have severe movement or psychiatric disorders. The size of the generated lesion can to some extent be controlled by RF-generator settings such as temperature and time as well as the electrode configuration. Today, MR- imaging and CT are the essential diagnostic methods to confirm the lesion size in vivo. The aim of this study was to investigate whether it is possible to use changes in the reflected light intensity and laser Doppler flowmetry as a marker for size estimation during RF-lesioning.

Keyword
Brain electrodes, Laser doppler flowmetry, Reflection spectroscopy, RF-lesioning
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-47497 (URN)10.1117/12.427930 (DOI)
Conference
Biomedical Diagnostic, Guidance, and Surgical-Assist Systems III, San Jose, CA, January 20, 2001
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2016-05-04

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