INTRAVASCULAR MR TRACKING CATHETER - PRELIMINARY EXPERIMENTAL EVALUATION

OBJECTIVE. This article reports on the preliminary evaluation of a new technique for guiding intravascular interventional procedures with MR imaging. Active real-time position monitoring of catheters with MR im aging is made possible by incorporating a small RF coil into the tip o f the catheter, The purpose of this study was to evaluate the practica bility and localizing precision of this MR catheter tracking technique in vitro and in vivo in comparison with fluoroscopy. MATERIALS AND ME THODS. Feed cables employing a 0.9-mm-diameter coaxial cable, a 0.5-mm -diameter partially shielded coaxial cable, and a twisted pair cable a ttaching RF coils at the catheter tip to a coaxial plug at the cathete r base were assessed. Further, miniature copper loop RF coils of two, three, and four turns were tested, In vitro validation of MR tracking was achieved by using a phantom consisting of a water-filled harvested segment of human aorta and iliac arteries embedded in gel. Accuracy o f catheter placement was compared with MR and fluoroscopy. Subsequentl y, the MR tracking technique was evaluated in a swine model using a pr ototype B-French MR tracking catheter. RESULTS. A fully shielded coaxi al cable was found to be crucial for localizing the attached RF coil b y means of the tracking technique. The number of coil turns had a less er impact. Positions of the catheter tip measured with the MR techniqu e and with fluoroscopy correlated well (r > .98), with a 6-mm 95% conf idence interval of positional differences. Active real-time tracking o f the coil-tipped catheters was achieved both in vitro and in vivo. Th e 5-French tracking catheter was successfully placed in the splenic an d renal arteries of the swine. CONCLUSION. Robust in vivo tracking and accurate placement of catheters equipped with miniature RF coils are possible with MR imaging.