Development Of Controllable Electrolysis Detachable Coil (LLC)

The purpose of this studies is to develop a new coil system(LLC) used to embolize cerebral aneurysms as well as other vascular diseases in central nervous system. The special character of this coil system is that it can be detached at any point of coils when it is positioned satisfactorily by electrolysis. This special character make users avoid some shortcomings to use all of the commercial coil systems including GDC and MDS.Our investigation consist of three parts. The first step is to select some proper materials to make coils. The second part is to evaluate the characters of LLC. The last part is to evaluate short-term reliability to occlude the aneurysmal model.We use chronopotentiometry to select the most aproprate material among seven metal and metal alloys which are currently used for make coils and stents (two kinds of Niti alloys, two kinds of platinum alloys, two kinds of stainless steels and pure tungsten). The results showed that Nitinol (superelasticity form) is the only material having all the characters we need. The mean electrolysis time is 92±77 seconds and 98±16seconds in vitro and in vivo respectively. There exist a significant positive relationship between the electrolysis time and the diameters of wires(p<0.0001). The optimal current is 2mA.To evaluate the characters of LLC include 1. The reliability of detaching the coils by electrolysis at any point of the coils in vitro and in vivo. 2. Memory effect and stability in pulsating vessels. 3.the friction of coils in the microcatheter. 4.MR compatibility and X-ray opacity. We evaluat the mechanical and electrochemical characters of LLC in vitro and in vivo. The results showed that the coils can be cut with 2mA current at any point and the rupturing point always locate at the tip of microcatheter. The mean cutting time is 15.49 and 13.76 minutes in vitro and in vivo respectively. This time is much longer than the time of cutting a single wire. We consider the reason is that the outer diameter of coils is much larger that a single wire. The second reason is that the ruptured points at the tip of the catheter are multiple for...