Modeling radiofrequency heating of embolization coils for the treatment of cerebral aneurysms

Abstract

The deterioration of the arterial wall may result in the ballooning or widening of the artery which is called aneurysm. Untreated aneurysms in the brain may rupture and cause subarachnoid hemorrhage (SAH) and in some cases, stroke. Coil embolization is a treatment for cerebral aneurysm which was introduced by Guido Guglielmi. In this method, a catheter is guided into the brain in order to insert small platinum coils inside the aneurysm so as to occlude the area. One problem is that the occluded aneurysm can be recanalized after some months. One of the hypotheses is that recanalization originates from the endothelium and that endothelial denudation can prevent recanalization.
Dr Jean Raymond (CHUM) has suggested that radiofrequency energy could be an effective method for endothelial denudation. Our project is to investigate the effects of radiofrequency current applied to a platinum coil on the temperature distribution of brain tissue. The finite element method is used to compute the current distribution in the tissue surrounding a simple coil; the dissipated power density is used to compute the temporal evolution of the temperature distribution. Temperature measurements performed in a similar tissue phantom are used to validate the model. We found that radiofrequency current cannot be delivered directly to the coil because of its high electrical resistance which produces an inhomogeneous temperature distribution. However, by injecting radiofrequency current into an electrode placed at the center of the coil, a homogenous and predictable temperature distribution can be obtained. The effects of the length and width of the electrode were investigated so as to identify an optimum configuration.