ULTRASONIC WAVE DISTORTION MEASURMENT AND CORRECTION

这个项目的总体目标是改善观点和反差 临床超声成像系统分辨率的发展 自适应聚焦技术。这项研究的具体目的是 测量通过组织路径传播产生的波前失真， 为了表征与这种失真相关的焦点退化， 根据已知的超声和组织路径计算传播 组织的形态特征，并评估现有的方法和 开发改进的自适应聚焦方法以消除脉冲失真。 脉冲传输和脉冲回波测量将使用 二维光圈和专用定制实验装置 将散射源或散射体区域成像。时间延迟差， 能级变化、波形形状变化以及一阶 因为波前失真的二阶统计量将由 测量结果。这些测量还将被用来表征 通过组织路径传播而产生的聚焦和图像退化。 所有的测量都将使用新鲜的腹壁样本， 获得胸壁、脂肪、肝脏、肌肉及其适当的层 在尸检过程中，以及从手术中获得的脂肪和乳房。 波前失真的计算 将制作传输中的组织路径和脉冲-回波配置 使用抛物线近似。在这些计算中， 组织的不均匀性将由将被 也是从组织标本的大体和组织分析中构建的 就像超声波测量一样。可用的自适应对焦技术 为了消除脉冲失真，将对脉冲失真进行严格的研究 已评估。将开发改进的自适应聚焦技术 通过使用从波前失真获得的信息 测量和计算。透彻的分析、统计总结、 以及比较在包括每个特定的 我们的目标是制定有关影响的量化结论。 临床超声成像系统中波前失真的研究 纠正这些扭曲的可能性。数据分析将 提供能够从扩展的有用信息提高分辨率的信息 光圈。自适应将获得进一步提高的分辨率 在这项研究中开发的聚焦技术。结果在意料之中 为显著提高能力奠定基础 超声可以区分正常组织和病变组织 在目前不可能的情况下确定疾病的严重程度。

The general objective of this project is to improve the point and contrast resolution of clinical ultrasonic imaging systems by the development of adaptive focussing techniques. The specific aims of the research are to measure wavefront distortion produced by propagation through tissue paths, to characterize focus degradation associated with this distortion, to calculate propagation through tissue paths based on known ultrasonic and morphologic properties of tissue, and to evaluate existing methods and develop improved methods of adaptive focussing to remove pulse distortion. Pulse-transmission and pulse-echo measurements will be performed using a two-dimensional aperture and a specialized custom experimental apparatus to image a source or a region of scatterers. Time delay differences, energy level variations, waveform shape changes, and first-order as well as second-order statistics of wavefront distortion will be determined from the measurements. The measurements will also be used to characterize the focus and image degradation produced by propagation through a tissue path. All of the measurements will employ fresh specimens of abdominal wall, chest wall, fat, liver, muscle, and appropriate layers thereof obtained during autopsy as well as fat and breast obtained from surgery. Calculations of the wavefront distortion caused by propagation through a tissue path in transmission and pulse-echo configurations will be made using a parabolic approximation. In these calculations, the effect of tissue inhomogeneities will be represented by phase screens that will be constructed from gross and histologic analysis of tissue specimens as well as from ultrasonic measurements. Available adaptive focussing techniques for the removal of pulse distortion will be investigated and critically evaluated. Improved adaptive focussing techniques will be developed through the use of information obtained from the wavefront distortion measurements and calculations. A thorough analysis, statistical summary, and comparison of data obtained in studies comprising each of the specific aims will be made to develop quantitative conclusions about the influence of wavefront distortion in clinical ultrasonic imaging systems and the potential for correction of these distortions. The data analysis will provide information that enables improved resolution from expanded useful apertures. Further improved resolution will be obtained from adaptive focussing techniques developed in this research. The results are expected to provide a foundation for a significant increase in the capability of ultrasound to distinguish between normal and diseased tissue and to determine the severity of disease in circumstances not currently possible.