Abstract
Recent studies show the benefit of megahertz-frequency ultrasound in diagnosis and therapeutic purposes. However, it has not been enough to estimate the biological safety and dose limitation of high-frequency ultrasound for medical use. Here we have studied the biological effect of ultrasound at low-megahertz frequencies on the cells. For an ultrasound apparatus, piezoceramic transducers of 1.0 MHz and 2.4 MHz were used and placed in the bottom of water tank made of brass. A glass tube for irradiation containing 2.0 ml sample was set above the transducer on the water. The intensity of ultrasound for the frequencies ranging from 1 MHz to 8 MHz at the position of placed tube was determined by calorimetry and KI dosimetry, which was also verified with ultrasonic hydrophone (NH8114, Toray Engineering). Reproductive cell death was measured for three days after irradiation. Each effect of irradiated cells was compared at constant value of ultrasound intensity with 10-seconds exposure in all frequencies. We intend to report biological effect of ultrasound at low-megahertz frequencies on human lymphoma U937 cells.
