Physics of ultrasonic surgery using tissue fragmentation: Part I.

The ultrasonic surgical aspirator employs a vibrating metal tip to fragment tissue and then aspirates the debris through the hollow center of the tip. The mechanism of interaction has been stated to be poorly understood, most likely related to cavitation, possibly in concert with other mechanical actions. In Part I (of two parts), the role of stroke, suction, frequency, tissue type and tip area are examined with regard to tissue fragmentation rate. A tissue quantifier which can be used to relate the performance of the ultrasonic aspirator and a selected tissue is described. Suction is shown to make a significant contribution to the interaction. Thermal and tip load experiments are used to estimate the acoustic pressures and powers at the tip. In Part II, photographic and acoustic data from experiments in water and on a range of fresh pig tissues are used to further investigate the fragmentation effect.