FLEXIBLE MAGNETOHYDRAULIC ACOUSTIC CATHETER

IT IS POSTULATED THAT INTENSE (> 3 W/MM2) ACOUSTIC VIBRATION CAN BE CONVEYED WITH SUFFICIENT INTENSITY THROUGH A FLEXIBLE CONDUIT TO INTRAVASCULARLY EXCAVATE ATHEROSCLEROTIC PLAQUE. THE SYSTEM TO BE EVALUATED CONSISTS OF: (1) AN ACOUSTIC TRANSDUCTION CAVITY CONTAINING A MAGNETOSTRICTIVE PISTON TRANSDUCER THAT IS EXCITED BY AN EXTERNAL MAGNETIC FIELD, (2) A STAINLESS STEEL REINFORCED CATHETER ONE METER IN LENGTH THAT IS CONNECTED TO THE TRANSDUCTION CAVITY AND (3) AN METAL TIP WHICH TERMINATES THE CATHETER. THE TRANSDUCER SELECTED IS CAPABLE OF PRODUCING CONSTANT EXTENSION OVER THE FREQUENCY RANGE 0 TO 30 KHZ. WITHIN THIS FREQUENCY REGIME PERFORMANCE OF SYSTEM WILL BE EVALUATED BY MICROSCOPIC MEASUREMENT OF TIP MOTION. AMPLITUDE OF TIP MOTION (FM) AS A FUNCTION OF FREQUENCY (HZ), AND ROOT MEAN SQUARE TRANSDUCER MAGNETIZATION (A/M). THE ABILITY OF CATHETER TIP VIBRATION TO PENETRATE AND EXCAVATE PLAQUE IN-VITRO WILL BE EVALUATED IN TERMS OF TIP PENETRATION RATE (FM/S), TIP VIBRATION AMPLITUDE (FM) AND FREQUENCY (HZ). DISSECTED SPECIMENS WILL BE SECTIONED AND HISTOLOGICALLY EXAMINED FOR PERFORATION OF THERMAL EFFECT TO THE INTIMA. MEAN PARTICLE SIZE OF DISSECTED SPECIMENS WILL BE MICROSCOPICALLY GAUGED. TIP SURFACE TEMPERATURE WHEN VIBRATING IN FREE AIR AND DURING DISSECTION BE OBTAINED PYROMETRICALLY.