BIEN 557, Medical Ultrasonics

Fall 2004

Steven A. Jones

Term Project Topics

Each of these projects will require a combination of the understanding of the Doppler process, mathematical analysis, and the extraction of information from available literature (in the library). Choose one concept and work on it in a group of 2 people.

1. Obtain a schematic of a Doppler ultrasound transceiver circuit, and directly relate each component of the system to the simplified diagram provided in the Review Article.

2. Determine the FDA regulations on ultrasound transmission levels for medical devices. How do the limitations on transmitted power depend on the application? Use all necessary information on voltage-to-acoustic energy conversion, including the transfer function of a real ultrasound transducer, and determine how the transmitted energy is related to the input voltage.

3. Obtain information on the transfer function of a typical ultrasound transmitter. If a single pulse (delta function) is input into the transducer, what would be the shape of the output signal? What voltage input would be necessary to obtain a sample volume that has a Gaussian shape in the axial direction?

4. Obtain the equations that describe a 3-dimensional system that is designed to determine the complete vector representation of velocity. Describe, mathematically, the expected error in the velocity vector as a function of the separation angles of the three probes with respect to that vector.

5. Assuming that you have a completely noise-free Doppler ultrasound system (in the sense that there is no additive noise – there is still ambiguity noise), derive an equation that relates the velocity estimate error, the measurement time, the velocity value, and the sample volume size. You will have to include other variables, of course, such as speed of sound, and Doppler angle.

6. Describe the attenuation of a Doppler pulse mathematically, using values for scattering and attenuation available in the literature. Can you show that a 2 MHz probe is appropriate for transcraneal Doppler, a 5 MHz probe is appropriate for cardiac Doppler, a 10 MHz probe is appropriate for carotid Doppler, and a 20 MHz probe is appropriate for intra-arterial Doppler measurements? You will need to consider how small the returned signal can be before its detectability is compromised.

It is expected that your final report will be about 15 pages long. Use the standard: Abstract, Introduction, Methods, Results, Discussion, Conclusion format.