Nonlinear Acoustics in Calibration/Metrology of High Intensity Focused Ultrasound

高强度聚焦超声校准/计量中的非线性声学

• 批准号: 7582520
• 负责人: Vera Khokhlova
• 金额: $ 48.1万
• 依托单位: UNIVERSITY OF WASHINGTON
• 依托单位国家: 美国
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-09-15 至 2012-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7582520
• 关键词: Acoustics; Address; Adoption; Algorithms; Animals; Calibration; Clinic; Clinical; Communities; Condition; Data; Depth; Development; Devices; Evaluation; Experimental Models; Face; Fiber Optics; Focused Ultrasound Therapy; Frequencies; Furuncles; Heat-Shock Response; Heating; Heterogeneity; Holography; Industry; Invasive; Laboratories; Lesion; Manufacturer Name; Measurement; Measures; Methods; Metric; Microbubbles; Modeling; Monitor; Morphologic artifacts; Non-linear Models; Operative Surgical Procedures; Output; Patients; Photography; Population; Procedures; Public Health; Radiation; Range; Rate; Recommendation; Reporting; Research; Role; Safety; Shock; Source; Speed; Spottings; Standards of Weights and Measures; System; Techniques; Temperature; Testing; Therapeutic; Therapeutic Uses; Thermometry; Time; Tissue Sample; Tissues; Today; Transducers; Ultrasonic Therapy; Ultrasonic Transducer; Ultrasonography; Uncertainty; United States Food and Drug Administration; Water; Work; absorption; attenuation; base; clinically relevant; improved; in vivo; metrology; millisecond; pressure; research study; response; simulation; size; sound; tissue phantom; tool; transduction efficiency; vapor

DESCRIPTION (provided by applicant): High Intensity Focused Ultrasound (HIFU) is used to perform surgical procedures non-invasively by using high amplitude focused sound waves to induce irreversible tissue damage within a mm-size focal `hot spot.' HIFU is rapidly gaining widespread clinical use and is poised to reach even broader patient populations. However, there has been a rising concern within all parts of the HIFU community that no standards exist for measuring or reporting of HIFU fields. It has been also realized that the relation between HIFU output and the produced bioeffects is poorly understood. This lack of standards and relations of acoustics to bioeffects is a major impediment to broad clinical adoption of HIFU. The proposal addresses this current gap in development of such standards as well as understanding the bioeffect mechanisms. Nonlinear acoustics is the study of high amplitude sound. Nonlinear acoustic propagation leads to shocks, discontinuities in the acoustic wave, which encompass a very broad range of frequencies. Shock formation and strong focusing distinguish HIFU from other medical ultrasound approaches and combine to make accurate measurements difficult. Also, since ultrasound energy losses that create heating are frequency dependent, the relatively high absorption in tissue counteracts nonlinear propagation, which means that no simple way exists to extrapolate water measurements directly to tissue. Since the broadest frequency content is in the shocks, absorption at the shocks is the critical mechanism of tissue heating. The specific aims of this proposed project are: (1) Use combined simulations and measurements to determine the high amplitude acoustic output of HIFU sources in water. (2) Determine the fields in tissue phantoms and tissue and define methods to derate water measurements to tissue. (3) Quantify the mechanism of enhanced tissue heating due to nonlinear acoustics and corresponding bioeffects in ex-vivo tissue and in vivo animal studies (4) Synthesize results of Aims 1-3 into practical recommendations for characterization of HIFU devices to improve regulatory oversight, understanding bioeffects, and efficacy and safety of clinically relevant HIFU therapeutic devices. Our method is a combined approach of numerical simulation and experimental measurement. Our model includes nonlinear acoustic propagation effects, diffraction, absorption, and tissue heterogeneities. Our acoustic measurements tools include small broad bandwidth hydrophones and a new step-shock source to calibrate the hydrophones. Our thermal measurement techniques involve the noninvasive observation of boiling with high speed photography and active and passive acoustic transducers. Tissue phantoms, excised and in vivo tissue will be used in experiments and modeling. This proposed work will benefit public health by providing tools and recommendations to help regulate and control HIFU exposures, which will improve efficacy and safety and facilitate a more rapid clinical acceptance of this promising therapy. PUBLIC HEALTH RELEVANCE: High Intensity Ultrasound (HIFU) is gaining wider acceptance in the clinic as a form of noninvasive or minimally invasive surgery. However, no agreed system for calibration of HIFU output currently exists today. This proposed work will benefit public health by providing tools and recommendations to help regulate and control HIFU exposures which will improve efficacy and safety and facilitate a more rapid clinical acceptance of this promising therapy.

描述（由申请人提供）：高强度聚焦超声（HIFU）用于通过使用高振幅聚焦声波在mm大小的焦点“热点”内诱导不可逆的组织损伤来进行非侵入性外科手术。“HIFU正在迅速获得广泛的临床应用，并有望达到更广泛的患者群体。然而，在HIFU社区的所有部分中，存在用于测量或报告HIFU场的标准的问题日益增加。人们还认识到，对HIFU输出和所产生的生物效应之间的关系知之甚少。这种标准的缺乏和声学与生物效应的关系是HIFU广泛临床应用的主要障碍。该提案解决了目前在制定此类标准以及理解生物效应机制方面的这一差距。非线性声学是研究高振幅声音的学科。非线性声传播导致冲击，声波中的不连续性，其包含非常宽的频率范围。冲击形成和强聚焦使HIFU与其他医学超声方法区别开来，并且联合收割机使精确测量变得困难。此外，由于产生加热的超声能量损失是频率相关的，组织中相对高的吸收抵消了非线性传播，这意味着不存在将水测量值直接外推到组织的简单方法。由于最宽的频率内容是在冲击，吸收冲击是组织加热的关键机制。本课题的具体目标是：（1）采用模拟和测量相结合的方法确定水中HIFU源的高振幅声输出。(2)确定组织体模和组织中的场，并定义降低组织水测量值的方法。(3)量化离体组织和体内动物研究中非线性声学引起的组织加热增强机制和相应的生物效应（4）将目标1-3的结果综合为表征HIFU设备的实用建议，以改善监管监督、了解生物效应以及临床相关HIFU治疗设备的有效性和安全性。我们的方法是数值模拟和实验测量相结合的方法。我们的模型包括非线性声传播效应，衍射，吸收和组织的异质性。我们的声学测量工具包括小型宽带水听器和用于校准水听器的新阶跃冲击源。我们的热测量技术包括用高速摄影和主动和被动声换能器对沸腾进行非侵入性观察。将在实验和建模中使用组织模型、切除组织和体内组织。这项拟议的工作将通过提供工具和建议来帮助调节和控制HIFU暴露，从而使公众健康受益，这将提高疗效和安全性，并促进这种有前途的治疗方法更快地被临床接受。公共卫生关系：高强度超声（HIFU）作为一种无创或微创手术形式在临床上获得了更广泛的认可。然而，目前不存在用于校准HIFU输出的商定系统。这项拟议的工作将通过提供工具和建议来帮助调节和控制HIFU暴露，从而提高疗效和安全性，并促进这种有前途的治疗方法更快地被临床接受，从而使公众健康受益。