a silicon rubber embolization agent used in general as well as cerebral vascular surgery having a component a which is composed of : a linear , low viscosity polysiloxane selected from the group consisting of dialkyl , alkylaryl , alkenylalkyl , and diarylpolysiloxanes having reactive functional groups selected from the group consisting of hydroxyl , acyloxyl , alkoxyl and amino ; a low viscosity cyclic dialkylpolysiloxane having the formula 4 , wherein r is alkyl ; a pharmaceutically acceptable iodo - containing organosilicium ; or a non - metallic , organic x - ray contrast material , and a component b which is a therapeutically acceptable cross - linking catalyst .