Ultrasound blood flow measurement via time-domain signal pattern correlation

Blood flow measurements by means of ultrasound time domain pattern correlation have been studied by many investigators. Assessing biological fluid flow with ultrasound time domain correlation algorithms has several advantages over conventional Doppler flow measurements. The main advantage is its higher spatial-resolution, which allows for greater accuracy when computing flow velocities. The achieved higher spatial resolution is accompanied by a higher computational demand associated with most available correlation algorithms. For this reason, several pattern correlation algorithms with lower computational demand are proposed in this research. The proposed algorithms are designed to achieve a comparable accuracy with less computational demand. The algorithms are verified analytically and applied to in-vitro blood flow measurements.; A major concern of time domain flow measurement is the retrieval of 2D flow velocities. The lack of lateral velocity information presented in Doppler systems is a major obstacle for obtaining exact velocity profiles in blood vessels. Different approaches have been taken to estimate the incident angle between the acoustic beam and the direction of blood flow. In this research, a two-probe flow measurement approach is investigated. This approach is similar to those of the two-slit optometric technique for monitoring the movement of red blood cells in the microcirculation and has been studied previously by this laboratory. To improve the accuracy of measurement, a commercially available contrast agent, Albunex{dollar}spcircler,{dollar} was injected into the flow so that a better signal to noise ratio can be achieved. The contrast agent has been proven to be non-toxic for human injection and studied both in-vitro and in-vivo. The measurement is further improved by estimating the arrival time difference of traced signal speckle with a cluster correlation algorithm. It has been shown from the experimental data and computer simulations that the proposed cluster correlation algorithm having advantages on improving both computational expense and probability of misregistration.; Efforts are also made to develop algorithms for two dimensional flow measurements. Two bit-pattern correlation algorithms are proposed to evaluate the arrival time from a pair of successive images. The algorithms are verified by in-vitro data taken from porcine blood samples with commercial ultrasonic scanners.