SHEAR-MODE TRANSCRANIAL ULTRASOUND IMAGING

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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.