Design characteristics for intravascular ultrasonic catheters

Several factors are important in the design of intracoronary ultrasonic imaging catheters. The mechanical considerations are first discussed and equations are developed for calculating the forces affecting catheter passage in a blood vessel. These equations are applied to the problem of Judkins (transfemoral) coronary artery catheterization, using previously described anatomical information and catheter moduli values. The introduction force is calculated for each position along the vessel for both a high and low value of estimated catheter-wall friction (coefficient values of 0.04 and 0.2, respectively). Next, the problem of catheter or transducer rotation is analytically described. The advantages of spiral drive cables with high torsional rigidity and low bending stiffness are numerically shown. Finally, several methods and considerations are given for electrical connection to the transducer. These results and equations should facilitate the design of intracoronary ultrasound imaging devices in the future.