Doppler ultrasound

• Main Author: Kiran Easwaran.
• Other Authors: Zhang Cishen
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering::Electrical and electronic engineering::Control and instrumentation::Medical electronics
• Online Access: http://hdl.handle.net/10356/17846
• Institution: Nanyang Technological University

Ultrasound imaging is widely used in medicine. It is possible to perform both diagnosis and therapeutic procedures with this imaging technique. Medical ultrasonography is used in various applications in medicine including Cardiology, Endocrinology, Gastroenterology, Gynecology,Obstetrics, Ophthalmology, Urology and many more. Diagnostic Ultrasound has since been imported into practically every other area of medicine. Sonography can be enhanced with Doppler Measurements which employ the Doppler Effect to assess whether structures (usually blood) are moving towards or away from the probe and its relative velocity. By calculating the frequency shift of a particular sample volume, for example a jet of blood flow in the minor arteries in the arms, its speed and direction can be determined and visualized. In this particular project, the focus is on acquiring the raw data and processing it with several methods to get a proper image of the blood flow. These methods are, the arrangement of the raw data in a matrix format, Hilbert transform this to acquire a real and imaginary part for use later with a type of clutter filtering as well as Autocorrelation. Clutter filtering is used to segment the slow moving tissues from the blood. Autocorrelation which is the main method involved is used to find the Doppler frequency shift. In fact Autocorrelation relates similar patterns, in this case, Doppler frequency shifts. Smoothing, thresholding as well as Colormapping is performed to get the final image.