工藤 信樹

Nobuki KUDO

北海道大学大学院情報科学研究院

Faculty of Information Science and Technology, Hokkaido University

キーワード : biological effects, ultrasound safety, cavitation, non-thermal effects, ultrasound therapy

超音波の生体作用は，熱的作用と非熱的作用に分けられる．非熱的作用には，超音波の圧力が直接作用を及ぼす一次的効果と，超音波によって生じたキャビテーションが作用を及ぼす二次的効果がある．本文では，キャビテーションの二次的効果に注目し，超音波照射下における気泡のダイナミクスと，気泡が生体に作用を与える機序について解説する．また，超音波診断とＸ線診断が生体作用を生じる機序を比較し，キャビテーション現象に注目することの意議を明らかにする．さらにキャビテーションの作用を積極的に利用する治療法を紹介し，治療分野における超音波応用の有用性を明らかにする．

The biological effects of ultrasound exposure can be categorized into thermal and non-thermal effects. Non-thermal effects include primary effects that are directly induced by ultrasound pressure and secondary effects that are generated by ultrasonically induced cavitation phenomena. This tutorial has been written to provide a better understanding of the secondary effects of ultrasound exposure. The dynamics of cavitation bubbles under ultrasound exposure are described to show the mechanisms by which the dynamics of bubbles cause biological effects. The mechanisms are also discussed by comparing ultrasound and X-ray imaging and showing key features of cavitation phenomena in induction of biological effects. Ultrasound therapies that mainly utilize cavitation mechanisms are introduced to show the importance of ultrasound therapies in current and future medicine.