ARTERIAL PROPERTIES FROM STIMULATED ACOUSTICAL EMISSION

组织的低频材料特性，如硬度或 移动性，已被证明与疾病有关，如 动脉粥样硬化和肿瘤。这项计划的长期目标是 生产低频材料的测量和成像方法 使用高分辨率和对比度的生物组织的特性 我们的新的超声激励声发射方法。由此产生的 动脉僵硬的非侵入性测量将适用于研究 在人口数量上。在目前提出的计划中，我们追求的目标是 切除后钙化与非钙化胎盘的检测与成像 动脉，以及在动物模型中，使用一种成像技术 声发射将物体的机械响应映射到局部 干涉超声束产生的循环辐射力。这个 我们方法的新奇之处在于检测到组织的诱导运动 由于其声发射导致对位移的敏感性 几个埃的量级。这种我们称之为“超声波”的方法 受激声发射(USAE)“，似乎非常适合这两个微型 钙化的检测和宏观检测，硬组织较少。 该方法是由超声辐射压力刺激产生的 使用双光束或共焦换能器几何形状的振动。这 程序研究切除的人和活体猪的动脉， 没有疾病，将USAE图像和光谱与组织学进行比较 对动脉的分析。初步结果清楚地勾勒出 USAE图像中钙化、非钙化和正常动脉段 在声发射频率从7千赫到41千赫的范围内获得。 使用非侵入性仪器及早发现动脉粥样硬化 例如配备有超声刺激的现代超声扫描仪 声发射，将提供一种有用的方法来描绘非 有症状的动脉粥样硬化患者的新生疾病来自于 没有这种全身性的隐匿性疾病。成功完成这项工作 计划将导致USAE方法立即适用于 临床研究。

Low-frequency material properties of tissues, such as stiffness or mobility, have been shown to be associated with diseases such as atherosclerosis and neoplasms. The long-term goal of this program is to produce methods for measuring and imaging low-frequency material properties of biologic tissues with high resolution and contrast using our novel ultrasound stimulated acoustic emission method. The resulting noninvasive measures of arterial stiffness would be amenable to studies in populations. In the currently proposed program we pursue the goal of detecting and imaging calcified and non-calcified placque within excised arteries, and in animal models, with an imaging technique that uses acoustic emission to map the mechanical response of an object to local cyclic radiation forces produced by interfering ultrasound beams. The novelty of our approach is that the induced motion of tissue is detected by its acoustic emission resulting in a sensitivity to displacement of the order of a few Angstroms. The method, which we call "Ultrasonic Stimulated Acoustic Emission (USAE)", appears well suited to both micro- detection and macro-detection of calcification and less hard tissues. The approach results from ultrasonic radiation pressure stimulation of vibration using dual beam or confocal transducer geometries. This program studies excised human and in vivo swine arteries, with and without disease, comparing USAE images and spectra to histologic analyses of the arteries. Preliminary results clearly delineate calcified, non-calcified, and normal arterial segments in USAE images obtained at acoustic emission frequencies ranging from 7 kHz to 41 kHz. Very early detection of atherosclerosis using a noninvasive instrument such as a modern ultrasound scanner equipped with ultrasonic stimulated acoustic emission, would provide a useful method of delineating non- symptomatic atherosclerosis patients with nascent disease from those without this systemic occult disease. Successful completion of this program will result in USAE methods that are immediately applicable to clinical studies.