SHEAR-MODE TRANSCRANIAL ULTRASOUND IMAGING

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。子项目和研究者（PI）可能从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。所列机构为中心，不一定是研究者所在机构。该项目的目的是使用一种新的超声波方法，提供一种低成本，便携式的方法来成像血流，检测脑老化，并诊断某些脑部疾病。由颅骨引起的失真和低信噪比（SNR）严重限制了经颅多普勒等现有临床设备的使用。信号衰减是由颅骨的反射、折射、衰减和散射引起的。然而，我们最近的工作表明，在某些条件下，通过使用高入射角，可以通过颅骨传播超声，从而减少失真和提高信号幅度。数值和实验研究表明，这是由于在颅骨中诱导的剪切模式的行为。初步数据显示，通过颅骨以高角度获得的信号比纵向信号失真更小。我们正致力于通过作为与纵向声学模式相反的剪切波传播通过颅骨来实质性地改进经颅超声。这项研究正在测试经颅剪切模式在许多成像问题中的应用，包括血管检测、肿瘤检测、组织形态学和脑内的血管造影。这项工作可能提供一种非电离成像方法，可以在临床上操作，同时将一种新技术引入医学和生物成像。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The aim of the project is to use a new ultrasound method to provide a low cost, and portable methods for imaging blood flow, detecting hemorrhaging, and diagnosing certain brain disorders. Distortion and low signal to noise ratios (SNR) caused by the skull have severely limited the use of existing clinical devices such as trancranial Doppler. Signal degradation is caused by reflection, refraction, attenuation, and scattering by the skull. Our recentwork, however, indicates that under certain conditions it is possible to propagate ultrasound through the skull with reduced distortion and higher signal amplitudes by using high incident angles. Both numeric and experimental investigation indicate this is due to the behavior of shear modes induced in the skull bone. Preliminary data shows that a signal obtained through the skull at high angles is less distorted than a longitudinal one. we are working toward substantial improvement of transcranial ultrasound by propagating through the skull as a shear wave as opposed to a longitudinal acoustic mode. The investigation is testing the application of the transcranial shear mode to a number of imaging problems including the vessel detection, tumor detection, tissue morphology, and hemorrhaging in the brain. The work could potentially offer a non-ionizing imaging method that could in operate clinically, while introducing a new technique into medical and biological imaging.