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Modeling Radiofrequency Heating of Embolization Coils for the Treatment of Cerebral Aneurysm

Pariya Salami

Master's thesis (2010)

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Cerebral aneurysm is a weakness in the wall of a cerebral artery which causes a localized dilation or ballooning of the blood vessel. Untreated aneurysms in the brain may rupture and cause subarachnoid hemorrhage (SAH) and in some cases, stroke. Treatment may be surgical or endovascular treatments. The most popular endovascular treatment is coil embolization, first introduced with controlled detachment by G. Guglielmi in 1991. This method, which is currently used to treat approximately 80% of cerebral aneurysms, consists in inserting a catheter in the aorta and then guiding it to the desired region of the cerebral vasculature to insert small platinum coils inside the aneurysm. These coils induce clotting and occlude the aneurysms. A possible problem is that the occluded aneurysm can be recanalized after some months because of unknown reasons. Though the exact mechanism responsible for recanalization remains unclear, one of the hypotheses is that recanalization is related to the endothelium and that endothelial denudation can prevent recanalization. Some methods of denudation have been previously investigated, such as mechanical abrasion with the aneurismal neck-bridge device (ANBD) and cryoablation. Both methods showed undesirable results. The new method which is investigated in this memoir is radiofrequency ablation (RFA). Based on preliminary in vivo studies, it is believed that RFA can be effective in endothelial denudation and in improving the results of coil embolization. The main objective of our project is to investigate the effects of radiofrequency current applied to an endovascular platinum coil on the temperature distribution of perianeurysmal tissues so as to optimize the energy delivery process. To achieve this goal, inductive and resistive characteristics of the embolization coils, as well as the effects of the length and shape of the electrode on the temperature distribution was investigated using a computer modeling approach. In vitro experiments were also performed to validate the computer simulations. Based on this study, we conclude that platinum coils should not be used for the direct application of RF current. A steel applicator placed in the center of the endovascular coils is more appropriate. Also, an applicator length of 6 to 10 mm is optimized for generation of a uniform temperature distribution. Finally, animal studies should be performed to further investigate this promising approach.


L'anévrisme intracrânien est une déformation de la paroi d'une artère du cerveau qui provoque une dilatation localisée du vaisseau sanguin. Les anévrismes non traités peuvent se déchirer et causer une hémorragie sous-arachnoïdienne (SAH) et, dans certains cas, des accidents vasculaires cérébraux. Les traitements courants sont la chirurgie et les traitements endovasculaires. Le traitement endovasculaire le plus populaire est l'embolisation à l'aide de spirales qui a été proposée par G. Guglielmi en 1991 (ces spirales sont des endoprothèses vasculaires ayant la forme arrondie d'un ressort). Cette méthode, qui est actuellement utilisée pour traiter environ 80% des anévrismes cérébraux, consiste à insérer un cathéter dans l'aorte, puis à le guider vers le vaisseau désiré de façon à insérer des spirales de platine à l'intérieur de l'anévrisme. Ces spirales induisent une coagulation puis l'obstruction de l'anévrysme. Un problème possible est que l'anévrisme ainsi traité peut se recanaliser après quelques mois pour des raisons inconnues. Bien que les mécanismes de la recanalisation demeurent incertains, l'une des hypothèses est que celle-ci provient de l'endothélium et que la dénudation endothéliale pourrait prévenir cette recanalisation. Certaines méthodes de dénudation endothéliales ont déjà été étudiées, telles que l'abrasion mécanique avec le dispositif col-pont anévrismal (aneurismal neck-bridge device, ANBD) et la cryoablation. Ces deux méthodes ont toutefois présenté des résultats non désirés. La nouvelle méthode qui est étudiée dans ce mémoire est l'ablation thermique par courant radiofréquence (radiofrequency ablation, RFA), qui a été suggérée par J. Raymond.

Department: Institut de génie biomédical
Program: Génie biomédical
Academic/Research Directors: Pierre Savard and Jean Raymond
PolyPublie URL: https://publications.polymtl.ca/380/
Institution: École Polytechnique de Montréal
Date Deposited: 29 Nov 2010 14:27
Last Modified: 11 Nov 2022 10:30
Cite in APA 7: Salami, P. (2010). Modeling Radiofrequency Heating of Embolization Coils for the Treatment of Cerebral Aneurysm [Master's thesis, École Polytechnique de Montréal]. PolyPublie. https://publications.polymtl.ca/380/


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