ASSESSMENT OF CAVITATION FROM DIAGNOSTIC ULTRASOUND

通过超声诊断评估空化

• 批准号: 3178258
• 负责人: ROBERT E APFEL
• 金额: $ 25.49万
• 依托单位: YALE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1985
• 资助国家: 美国
• 起止时间: 1985-09-01 至 1996-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3178258
• 关键词: Anura; biomedical equipment safety; free radical oxygen; human subject; imaging /visualization /scanning; radiation hazard; ultrasonography; ultrasound biological effect

The use of diagnostic ultrasound in medicine has expanded enormously over the past few years and has become a vital clinical tool in the diagnosis and assessment of a large variety of ailments and conditions. There has been a steady evolution in the complexity and sophistication of the imaging and Doppler modalities that provide the principal instrumental tools for clinicians. These devices have tended, in general, to evolve to higher working frequencies to improve resolution, and consequently, because of the higher attenuation, to larger acoustic intensities and pressure amplitudes. There are two principal mechanisms whereby diagnostic ultrasound can interact with tissue with the potential for a bioeffect: a) a thermal mechanism resulting from absorption of the ultrasonic pressure wave and subsequent temperature elevation of the tissue; b) the phenomenon of acoustic cavitation in which relatively small amounts of energy are concentrated to microscopic scales, thus producing intense localized pressure and temperature. Concern for these potentialities has prompted concerted action by the FDA, American Institute for Ultrasound in Medicine, and NEMA to draft Output Display Standards for Real-Time Display of Thermal and Mechanical Indices. The current mechanical index (MI) is based on in vitro tests of the acoustical conditions for bubble nucleation in liquids containing prescribed bubble nuclei (polystyrene spheres and albumin-coated bubbles), as well as a theoretical model of the interaction of ultrasound with materials. Yet this work, though involving careful experimentation and theoretical efforts by many independent researchers, still cannot answer the question: Does diagnostic ultrasound produce bubbles in human tissue? The question has not been answered definitively because acoustical detection of micron-sized bubbles that last a microsecond is an extremely difficult task, especially if this transient, weak event is buried in the backscattered noise from blood cells, tissue inhomogeneities, etc. The proposed effort will couple the most sensitive bubble detection system with advanced signal processing techniques to determine the minimum conditions for acoustic cavitation inception in vivo. Of equal importance, yet not fully addressed thus far, is the question of the role played by the pulse duration and duty cycle of the acoustical imaging or doppler signal in determining bubble nucleation and activity, the latter being related, in all likelihood, to the degree of bioeffect that is possible when the mechanical index is exceeded. Thus, a systematic study of these parameter regimes is envisioned, for liquids, blood, and tissue equivalent phantoms. The above work on in vivo detection and duty cycle will be complemented by a continuation of studies of bioeffects induced in epithelia of frogs by diagnostic and therapeutic ultrasound, in order to understand better the formation of free radicals and the changes in ionic conductance that can potentially influence intracellular components.

诊断超声在医学中的使用已大大扩展 过去几年，已经成为诊断的重要临床工具 以及评估各种各样的疾病和条件。 有 在成像的复杂性和复杂性方面一直稳定发展 和多普勒模式，为主要工具工具提供 临床医生。 通常，这些设备倾向于发展到更高 工作频率以提高分辨率，因此， 更高的衰减，对较大的声学强度和压力振幅。 诊断超声可以有两种主要机制 与组织相互作用与生物效应的潜力：a）热效 吸收超声压力波和 随后的组织温度升高； b）现象 少量能量的声气水 集中在微观尺度上，从而产生强烈的局部化 压力和温度。 对这些潜力的关注引起了 美国超声研究所FDA的一致行动， 和NEMA用于实时显示热显示标准的NEMA显示标准 和机械指标。 当前的机械指数（MI）基于 体外测试液体气泡成核的声学条件 包含处方的气泡核（聚苯乙烯球和白蛋白涂层 气泡），以及超声相互作用的理论模型 与材料。 然而，这项工作虽然涉及仔细的实验 以及许多独立研究人员的理论努力，仍然无法 回答问题：诊断超声是否会在人类中产生泡沫 组织？ 由于声学 持续微秒的微米大小气泡的检测是极端的 艰巨的任务，尤其是如果将这种短暂的，薄弱的事件埋在 来自血细胞，组织不均匀性等的反向散射噪声。 拟议的努力将使最敏感的气泡检测系统与 高级信号处理技术以确定最低条件 用于体内的声气水。 同等重要，但不是 到目前为止，完全解决了脉搏扮演的角色的问题 声学成像或多普勒信号的持续时间和占空比 确定气泡成核和活性，后者是相关的 所有的可能性都达到了生物效应的程度 超过机械指数。 因此，对这些参数的系统研究 对于液体，血液和组织等效幻象，设想了机制。 上述有关体内检测和占空比周期的工作将由 继续研究青蛙上皮诱导的生物效应的研究 诊断和治疗性超声，以便更好地了解 自由基的形成和离子电导的变化可以 潜在影响细胞内成分。