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This study was designed to evaluate the feasibility of using cylindrical ultrasound transducers mounted on a catheter for the ablation of cardiac tissues. In addition, the effects of ultrasound frequency and power was evaluated both using computer simulations and in vitro experiments. Frequencies of 4.5, 6, and 10 MHz were selected based on the simulation studies and manufacturing feasibility. These transducers were mounted on the tip of 7-French catheters and applied in vitro to fresh ventricular canine endocardium, submerged in flowing degassed saline at 37°C. When the power was regulated to maintain transducer interface temperature at 90-100°C, the 10-, 6-, and 4.5-MHz transducers generated a lesion depth of 5.9±0.2 mm, 4.6±1.0 mm, and 5.3±0.9 mm, respectively. The 10-MHz transducer was chosen for the in vivo tests since the maximum lesion depth was achieved with the lowest power. Two dogs were anesthetized and sonications were performed in both the left and right ventricles. The 10-MHz cylindrical transducers caused an average lesion depth of 6.4±2.5 mm. In conclusion, the results show that cylindrical ultrasound transducers can be used for cardiac tissue ablation and that they may be able to produce deeper tissue necrosis than other methods currently in use.
Date of Publication: Feb. 1997