| A preliminary study for therapeutic application of phase change nano droplet (PCND) in combination with low frequency ultrasound was performed. With gel phantom, it was found that the presence of PCND enhanced temperature elevation induced by 1.1-MHz ultrasound using albumin as the indicator of protein coagulation. Not like 2.2-MHz ultrasound, coagulation volume increased drastically as exposure time prolonged, suggesting the increase of numbers of bubbles which are responsible for the temperature elevation. Acoustic signal analysis showed that very violent cavitation is induced when PCND and 1.1-MHz ultrasound used. Animal experiments with mice tumor tissues were also performed and it was found that tissue erosion and necrosis were simultaneously generated. Results obtained showed the potential usefulness of PCND for mixed mechanism (HIFU & cavitation) therapy. |