IN-VITRO EFFECTS OF HIGH-ENERGY PULSED ULTRASOUND ON HUMAN SQUAMOUS-CELL CARCINOMA-CELLS

Human squamous cell carcinoma cells cloned from the hypopharynx (FaDu) and oral cavity (SCC4) were exposed to high-energy pulsed ultrasound (HEPUS) in vitro to evaluate the effects of various physical parameter s on cell viability. Such included the number of pulses, voltage appli ed, pulse repetition rate and cell density. The experimental piezoelec tric ultrasound transducer used in the experiments generated pulses wi th a high negative pressure amplitude. By varying the repetition frequ ency from 0.6 to 8 Hz, cell viability was found to be least when pulse repetition was approximately 1 Hz. An increase in transducer voltage resulted in a linear decrease in cell viability. The cell survival rat e dropped exponentially as a function of the number of pulses applied, reaching 4.2% after 2000 pulses. The cell survival rate exhibited no significant dependence on cell density when cells ranged from 1 to 3.5 . 10(6) cells ml(-1). Data obtained with trypan blue dye exclusion we re confirmed by measurements of intracellular lactate dehydrogenase re leased into an extracellular fluid supernatant. By applying HEPUS to t umor cells, almost complete destruction of the cells could be achieved in vitro. The degree of cell destruction achieved depended significan tly on the number of pulses administered, the pulse repetition rate an d the transducer voltage applied.