ESTIMATION OF HYDROXYL FREE-RADICALS PRODUCED BY ULTRASOUND IN FRICKESOLUTION USED AS A CHEMICAL DOSIMETER

Hydroxyl free radicals produced in Fricke solution exposed to 80 kV X- rays or 23 kHz ultrasound (intensity 3 W cm(-2)) or 20 kHz ultrasound (intensity 18.9 W cm(-2)) or 3.5 M Hz clinical ultrasound (intensity 1 .47 W cm(-2)), as estimated from the Fricke dosimetric data, exhibited a linear dose-response relationship. The dosimeter was found to be ef fective in the concentration range 1.0-8.0 mM of FeSO4 solution. The h ydroxyl radicals produced in Fricke solution were inhibited by the OH radical scavengers dimethyl sulfoxide (200 mM), L-histidine (10 mM) an d sodium benzoate (10 mM) in a manner proportional to the rate constan ts of their reaction with the OH radicals. The power threshold for OH radical formation, which is presumably the threshold for cavity format ion, was estimated for 23 kHz ultrasound by this dosimeter as 1.28 W c m(-2) for a 4 cm(3) sample volume.