It is postulated that intense (greater than 3 W/mm2) acoustic vibration can be conveyed with sufficient intensity through a flexible fluid transmission line to intravascularly excavate atherosclerotic plaque. The system to be evaluated consists of: (1) an acoustic transduction cavity containing a Terbium Iron Dysprosium magnetostrictive piston transducer that is excited by an external magnetic field, (2) a 2 mm diameter hollow catheter made of stainless steel reinforced polyurethane tubing one meter in length that is connected to the transduction cavity and (3) an annular titanium tip which closes and terminates the catheter. A separate syringe, connected to the transduction cavity, provides static pressurization of the working fluid for suppression of gaseous and vaporous cavitation. The transducer selected is capable of producing constant 50 um p-p extension over the frequency range 0 to 30 KHz. Within this frequency regime performance of system at the natural resonant frequencies of the catheter fluid itself will be made by microscopic measurement of tip motion. Amplitude of tip motion (mm) as a function of frequency (Hz), root mean square transducer magnetization (H) and working fluid employed will be recorded. Water, glycerol, and light mineral oil will be evaluated as working fluids. The ability of catheter tip vibration to penetrate and excavate plaque in vitro will be evaluated in terms of tip penetration rate (mm/s), tip vibration amplitude (mm) 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
