MEASUREMENT OF ULTRASOUND FIELD IN INSONATION APPARATUS

Summary

The effect of ultrasound energy on biological systems is intensively investigated. The results of in vitro experiments cannot be objectively evaluated without the knowledge of the parameters of ultrasound field which the biological samples were exposed to. The aim of this work is to determine the intensity of ultrasound field in an apparatus which is used during ultrasound irradiation of biological samples. Biological samples are irradiated by a conventional therapeutic ultrasound device. The ultrasound field of the application head was measured first in ultrasonic measurement tank to determine a focal length of the head which is an optimum distance between the source of ultrasound and the Petri dish with the biological sample. The ultrasound intensity was measured using a needle hydrophone. Then we determined the ultrasound intensity distribution within the Petri dish. We measured ultrasound intensity within two planes parallel to the dish bottom. We revealed that the intensity distribution within the Petri dish is not uniform. We can conclude that spatial average ultrasound intensity in the centre of Petri dish reaches 10 – 40 % of the value set on the therapeutic device. Spatial average ultrasound intensity at the edge of Petri dish is approximately half compared to the value in the centre. However, it is possible to measure significantly higher values in local maxima of ultrasound intensity. The results of the measurements show that the value of the ultrasound intensity which is displayed on the therapeutic ultrasound device is not sufficient for the description of ultrasound field parameters in the insonation apparatus. The measurement of the ultrasound intensity is therefore the only one objective method of determination of these parameters.

Keywords:
ultrasound irradiation, ultrasound field, hydrophone