BIOEFFECTS OF GAS BODY ACTIVATION IN MEDICAL ULTRASOUND

医疗超声的安全考虑必然涉及 空化的非热机制。 如果气体最初 存在于生物介质中，那么特殊类型的超声波 发生称为气体体激活（GBA）的空化，并且可以是生物的- 在相对较低的暴露水平下非常有效。 在更高级别上， 发展成更剧烈的空化现象，伴随着自由的 自由基生成和声化学效应。 在哺乳动物中， 是一个微妙的现象，不常见，但潜在的重要性， 后果 气体体激活的物理学已经在 植物，昆虫和疏水中充满气体的微孔的研究 膜。 这项研究将通过评估新型气体来继续进行 包括蓝绿藻中的气泡在内的物体，超声造影 天然空化成核气体体， 存在于体外和体内。 关系的理论探讨 非热机制，如声流和自由 自由基，由此产生的生物效应的潜力将提供一般 具有预测效用的洞察力，超越了 实验 使用体外模型系统，例如充气的 将继续评估微生物的破坏能力， 流动剪切应力和空化的声化学产物 在培养的细胞中。 最后，生物物理学研究将于2010年启动。 用于测量GBA生物效应的哺乳动物模型系统 医学相关的条件。 这些跨学科研究是 仔细整合，重点阐明GBA的作用 和超声医学生物物理学中的空化现象。 自从奥- 哺乳动物体内空化现象的发生、作用和影响， 未知的，关于GBA生物效应潜力的基本信息是紧迫的- 这是风险评估工作所需要的。 生物效应的知识 气体体活化将有助于假设发展， 未来的哺乳动物和流行病学研究，并将有助于形成一个 临床情况下剂量测定和暴露标准的基础。

Safety consideration of medical ultrasound necessarily involves the nonthermal mechanism of cavitation. If bodies of gas are initially present in a biological medium, then the special type of ultrasonic cavitation called gas body activation (GBA) occurs and can be biological- ly effective at relatively low levels of exposure. At higher levels, GBA progresses into more violent cavitation phenomenon with associated free radical generation and sonochemical effects. In mammals, GBA is expected to be a subtle phenomenon with infrequent, but potentially significant consequences. The physics of gas body activation has been studied in research on plants, insects and gas-filled micropores in hydrophobic membranes. This research will be continued by assessing new types of gas bodies including gas vesicles in blue-green algae, ultrasonic contrast agents, and the natural cavitation-nucleating gas bodies which apparently exist in vitro and in vivo. Theoretical investigation of the relation between nonthermal mechanisms, such as acoustic streaming and free radicals, and the resulting potential for bioeffects will provide general insights with predictive utility beyond the specific conditions of the experiments. Use of in vitro model systems, such as the gas-filled micropore, will be continued to assess the damaging ability of micro- streaming shear stresses and of the sonochemical products of cavitation in cultured cells. Finally, biophysical studies will be initiated in mammalian model systems for the measurement of GBA bioeffects under medically-relevant conditions. These interdisciplinary studies are carefully integrated and focussed on the elucidation of the role of GBA and cavitation in the medical biophysics of ultrasound. Since the oc- currence, action and effects of cavitation in mammals remain virtually unknown, basic information on the potential for GBA bioeffects is urgent- ly needed for risk assessment efforts. Knowledge of the bioeffects of gas body activation will aid in hypothesis development for possible future mammalian and epidemiological studies, and will help to form a basis for dosimetry and exposure criteria in the clinical situation.