Microbubble-assisted Cavitation and Its Application to Ultrasonic Therapy
Date Issued
2006
Date
2006
Author(s)
Wang, Tzu-Yin
DOI
zh-TW
Abstract
Cavitation is the phenomena where cavities form and rapidly collapse within a liquid under intense pressure changes. The energy emitted during the cavitation process is likely to induce tissue damage. Therefore, the safety regulations for diagnostic ultrasound have been carefully established to minimize the risk of cavitational bioeffects. Nevertheless, well-controlled acoustic cavitation can also be an effective tool for noninvasive cancer therapy.
Our long-term goal is to integrate ultrasound diagnosis and therapy- to achieve localized cancer treatment by microbubble-assisted cavitation under safety regulations. This study is the first step to the long-term job. The inertial cavitation doses (ICDs) are measured and studied at a constant mechanical index (MI). The MIs vary from 0.06 to 0.79. The ICDs induced by 1.5-MHz signals, 3-MHz signals and a signal cascading a 3-MHz signal with a 1.5-MHz signal are not equal even if the three waveforms have the same MIs. It is believed that the is due to the fact that MI was defined on cavitation activities of free gas bubbles, but encapsulated bubbles were used in our experiments. Another reason is that MI is not directly related to the degree and amount of cavitation as ICD. As a result, MI may not be the best index to quantify acoustic cavitation. The use of MI as the only parameter to represent potential cavitation-induced tissue damage is also questionable and requires further investigation.
The in-house liposome microbubbles were used in the in vitro study on cavitational bioeffects. The quantitative study of liposome-assisted cavitation was conducted. An experimental system was built for the observation of the cavitation-induced cell damage to the human gastric cancer cell line, MKN45. Current results did not indicate a significant cavitation-induced cell death after one-minute exposure to ultrasound.
In the future, the ultrasound parameters need to be optimized and the recipe of the in-house liposome microbubbles also needs to be improved for higher stability and stronger ICD. The in vivo study will follow the in vitro experiments. A microdialysis perfusion system and a microlight-guide system will be used to monitor the efficacy of in vivo tumor treatment.
Subjects
超音波
微氣泡
穴蝕效應
機械參數
慣性穴蝕劑量
腫瘤細胞破壞
ultrasound
microbubbles
cavitation
mechanical index
inertial cavitation dose
cell toxicity
SDGs
Type
thesis
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