Shear wave based quantitative ultrasound imaging methods

基于剪切波的定量超声成像方法

• 批准号: RGPIN-2022-03729
• 负责人: Cloutier, Guy
• 金额: $ 3.64万
• 依托单位: Université de Montréal
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=764443
• 关键词: Shear; wave; based; quantitative; ultrasound

BACKGROUND: Clinical ultrasound (US) scanners typically provide brightness mode (B-mode) images where the acoustic impedance contrast between tissue structures is used to identify boundaries for diagnosis. Modern US systems also include Doppler modes (with or without contrast agents) for flow and tissue motion analysis, and elastography modes (strain and shear wave (SW) based) for assessing mechanical properties of tissues. Quantitative US (QUS) imaging is another field that aims at quantifying acoustic compression wave interactions with biological tissues. QUS techniques extract fundamental physical properties of tissues to provide information on sub-resolution properties that are not visible on B-mode or other imaging modes. STATE-OF-THE-ART POSITIONING: Since biological soft tissues are hydrated, viscoelasticity is suitable to represent their solid-like behavior using elasticity, and fluid-like behavior using viscosity. However, the assessment of elasticity through US imaging has been more often exploited than viscosity. In US elastography, SWs are usually generated through focused push beams followed immediately by the monitoring of the SW motion. Under certain assumptions, elasticity relies on the measurement of the SW speed, and viscosity on its frequency dispersion or SW attenuation. I will pursue the development of robust viscosity methods for SW elastography imaging. Also, based on intriguing preliminary data on changes in QUS backscatter properties during SW propagation, I am also proposing the development of a new field that I label: "Dynamic QUS backscatter imaging". OBJECTIVES: 1) Improve robustness of tissue viscosity assessment using SW propagation properties; 2) develop a new QUS concept based on SW propagation; 3) validate SW-based viscosity and QUS imaging methods using simulations, in vitro phantom data, and available in vivo human scans; and 4) develop an open-access simulation package combining SW tissue excitation and compression wave backscatter analysis for dynamic QUS backscatter imaging. HYPOTHESES: 1) SW attenuation imaging can be improved by allowing the spectral content of SWs to vary spatially, by no longer assuming a linear power law dependency for the attenuation, and by using a randomized sample consensus algorithm to seek attenuation versus distance in the framework of an optimization process. 2) The dynamic QUS backscatter method should reflect the correlation length of scatterers, which determines constructive and destructive compression wave interferences modulated by the SW propagation. The new dynamic QUS backscatter method may image local tissue oscillating scatterer size and position changes, and provide a new image contrast reflecting pathological states (different from standard backscatter QUS, SW speed, or SW attenuation). CONCLUSION: The development of SW-based technologies (viscosity and backscatter) should provide new imaging modalities for better biological tissue characterization.

背景：临床超声(US)扫描仪通常提供亮度模式(B模式)图像，其中使用组织结构之间的声阻抗对比来识别用于诊断的边界。现代超声系统还包括用于血流和组织运动分析的多普勒模式(使用或不使用造影剂)，以及用于评估组织机械特性的弹性成像模式(基于应变和横波(SW))。定量超声(QUS)成像是另一个旨在量化声学压缩波与生物组织相互作用的领域。QUS技术提取组织的基本物理属性，以提供在B模式或其他成像模式下不可见的亚分辨率属性的信息。最先进的定位：由于生物软组织是水合的，粘弹性适合用弹性来表示它们的固体行为，而用粘性来表示它们的流体行为。然而，通过超声成像对弹性的评估比粘度更常被利用。在美国弹性成像中，SWS通常是通过聚焦的推射束产生的，然后立即监测SWS运动。在某些假设下，弹性依赖于对短波速度的测量，而粘度取决于其频散或短波衰减。我将继续开发用于短波弹性成像的坚固的粘度方法。此外，基于有趣的初步数据，在短波传播过程中量子散射后向散射特性的变化，我还提议开发一个新的领域，我将其命名为“动态量子后向散射成像”。目的：1)利用短波传播特性提高组织粘度评估的稳健性；2)基于短波传播提出一种新的QUS概念；3)使用模拟、体外体模数据和活体人体扫描来验证基于短波传播的粘度和QUS成像方法；以及4)开发一个结合短波组织激发和压缩波背向散射分析的开放访问模拟包，用于动态QUS背向散射成像。假设：1)通过允许SWS的频谱含量在空间上变化，不再假设衰减与线性幂规律相关，并且通过在优化过程的框架中使用随机样本共识算法来寻求衰减随距离变化，可以改善SWS衰减成像。2)动态量子散射后向散射法应反映散射体的相关长度，这决定了西南传播调制的建设性和破坏性压缩波干扰。新的动态QUS背向散射方法可以成像局部组织振荡散射体的大小和位置变化，并提供反映病理状态(不同于标准背向散射QUS、短波速度或短波衰减)的新的图像对比度。结论：基于短波的技术(粘度和背向散射)的发展将为更好的生物组织定征提供新的成像方式。