Abstract: Electrolytic detachable coils have been used as main embolic materials for intracranial aneurysms. Liquid aneurysmal embolic materials represented by cellulose acetate polymer(CAP)are still controversial in use. In this research, the embolization result and pathological reaction after embolization of canine aneurysmal models with electrolytic detachable coils or CAP were observed. The comparison between the two materials might be helpful to explore the better one to improve the effect of intracranial aneurysms embolization. We made liquid material CAP, designed and constructed the self-made electrolytic detachable coils, which was named by Wu electrolytic detachable coil(WEDC). Canine aneurysmal models were constructed by anastomosis of venous pouches. The aneurysms were randomly grouped. The aneurysms were occluded with CAP and WEDC individually. Angiogram follow-ups were performed in 24 h, 2 weeks, and 2 months after embolization. The occluded aneurysms were dissected in each stage for light microscopic, electron microscopic, and histochemical research. We found that the result of embolization was significantly better with detachable coils than that with CAP(P<0.01). There was no complications related to embolization. But in CAP group with 12 aneurysmal models, the parent arteries were thrombosed or became stenosed after embolization in 4 aneurysms. Two CAP embolized aneurysms were ruptured in one week. Pathological examination showed that WEDC embolized aneurysms were filled with coils and loose thrombus around the coils and the CAP embolized aneurysms were densely packed with CAP mass 24 h after embolization. Acute chemical damage of the aneurysmal wall was found in early stage. The necks of aneurysms were gradually covered with newly formed endothelial layer and organization appeared inside the aneurysmal sac 2 weeks after embolization in both groups. Inflammatory cellular infiltration was much more prominent in CAP group than that in WEDC group. The damage to aneurysm wall in CAP group became more aggressive, and in some sections of the ruptured aneurysmal wall, the histological structure of aneurysmal wall was so badly damaged that no clear cell structure could be seen. Thrombus inside aneurysm was replaced completely by fibrous tissue and aneurysmal necks were covered with integrated endothelial tissue in both groups 2 months after embolization. But parts of coils might be exposed outside the endothelial layer in the coil embolization group. It is concluded that electrolytic detachable coils are still the most safe, efficient, and reliable method to embolize aneurysm. CAP should be improved greatly before it is widely used because of its difficulty to control and its strong chemical corrosion.

Key words: endovascular therapy, coils, cellulose acetate polymer