Project Definition The aim of this project was to design a steerable catheter, which would enable easier access to specific blood vessels. The design would be used in the Radiology Department for improved treatment of cerebral aneurysms in the brain. Additionally, a simulated arterial system was created for catheter testing and training.

Background Aneurysms are disorders that involve the localized widening of one or more blood vessels. It is estimated that 5% of the population has some type of aneurysm. There are no known ways to prevent aneurysms, but they are often treatable. The most common method used to treat an aneurysm is surgery. During surgery a catheter is inserted and guided into a specific blood vessel. The base of the aneurysm is closed off with clamps, sutures, coils, and other methods using catheters. Currently, catheter guidance techniques involve the use of various guide wires which can be very difficult and time consuming. The design of a steerable catheter would allow the surgeon to access hard to reach areas in less time.

Demands & Wishes zDemands yCatheter can turn up to 90° in any direction yCatheter diameter must be  1 mm in order to access arteries ranging in diameter from 2-3 mm yPerform within temperature range between 95°F and 105°F yPerform in various viscosity levels of the blood yPerform under various flow patterns and pulsatile natures of the blood yCatheter must not alter or harm the well being of the patient zWishes yCatheter should be relatively easy to handle and maneuver yPrice should be competitive with current catheters in the market

Calculations zWhat should the ratio of glycerol to water be to represent the viscosity of blood? Given:  blood  4cP, m  8 mol/kg, MW Glycerol = 92 g,  glycerol  1.1 g/cm 3 Solution: Volume of glycerol = (molality)(Molecular Weight)/(Density glycerol ) = Liters of glycerol/Liter of H 2 O zDetermination of Reynold’s Number (Ex. S.E.D. = 5): Given:  solution = 1.04 g/cm 3, Diam. = cm,  solution  4cP, Area = cm 2 Solution: Velocity (V) = Flow (Q)/ Area (A) = cm/sec Reynold’s Number (Re) = (  solution )(V)(D)/(  solution ) = 982…Laminar

Catheter Models z Model I consisted of a turn-wire threaded completely through the catheter and fastened to the end about in. down the outside of the catheter with silicon. z Model II is very similar to Model I except that the wire exits the catheter about 1 in. below the catheter tip where it is then fastened with silicon to the catheter head.

Catheter Models (cont.) z Model III followed the concept of Model II with the exception that the turn-wire floats freely outside the catheter to decrease the resistance between the wire and the catheter. To further this design, improvements must be done to guide the turn wire along the outside of the catheter. z Model IV* is currently under development, although proper materials are uncertain. The catheter design contains two types of tubing with varying stiffness connected by silicon. Again, a turn-wire is completely threaded through the catheter and attached with silicon to the catheter tip.The tube creating the catheter tip is more pliable than the other Suggestion from Dr. Bob Galloway

Catheter Models (cont.) z Model V will be created using Muscle-Wire technology. Muscle-Wire contracts when heated electrically past a threshold temperature. In this design, electrical wires attached to the Muscle-Wire run through the inside of the catheter. The Muscle-Wire is attached to the head of the catheter. Silicon will seal the head of the catheter to prevent liquid from entering.

Design Summary

Simulated Arterial System zOverview: yA closed-loop system, created from a reservoir, roller pump, and surgical tubing, allows the continual flow of a water and glycerol solution (providing Newtonian fluid characteristics) simulating blood within the arterial system. The model is approximately twice the size of the actual microvasculature (ID tubing = 6.3 mm). z Objectives: yTest prototypes of catheter designs yCreate an applicable learning device to further catheter insertion and guidance techniques* *Suggestion from Dr. Paul King

Uncertainties zCatheter Design yFeasibility of heating Muscle Wire in vivo yOptimal attachment positions of turn-wire on head of catheter yAppropriate materials for Model IV design z Arterial Model ySimilarity of surgical tubing in relation to actual arterial wall stiffness yLeakage at catheter insertion point yAccuracy of blood flow within cerebral vasculature

Future Work zFollow-up on uncertainties zContinue patent search zBuild and test additional prototypes zResearch the possibility of marketing the simulated arterial system for catheter training purposes zGRADUATE!