This project will continue research on a new method to analyze blood flow in deep tissues of the body which have slow blood flows and small volumes of movement using doppler ultrasound. In order to optimize the signal-to-noise ratio from these tissues a contrast agent, consisting of galactose microparticles that trap air bubbles, will be employed. Due to the nonlinear properties of this contrast agent, the doppler shifted second harmonic of the transmitted ultrasonic frequency will provide a signal with desirable properties for use in the system. At the second harmonic, the doppler shifted echoes from tissues not containing the contrast agent (surrounding tissues) will be reduced in comparison to tissues containing the agent (capillaries). The concept previously was tested using a mock flow system. It is now proposed to do in-vitro experiments using excised animal organs. The design of hardware which will allow the transmission of one ultrasonic frequency and the detection of the second harmonic of that frequency also is a part of the project. This research is extremely important since no other medical device is available to make such critical measurements. When fully tested and developed, this device should be able to compete in the medical imaging device marketplace.
