Date of Award
Doctor of Philosophy
Doppler ultrasound instruments have been used clinically for about 30 years and have proved to be highly reliable for the detection of arterial disease. In addition, a number of different Doppler instrument designs and techniques have been proposed to provide quantitative measurements such as volume blood flow, percent stenosis, and waveform indices. Before any measurement technique can be used, it must be validated.;We chose a two-pronged approach to the problem of evaluating Doppler ultrasound measurements of blood flow. We first developed a flow system that mimics the vasculature. The flow system comprises a computer-controlled pump, blood mimic, and a wall-less vessel phantom. A computer-controlled pump allows the production of accurate constant flow as well as pulsatile flow waveforms. The wall-less vessel phantom eliminates the artefacts introduced by the high attenuation and impedance mismatches of common vessel mimics such as latex rubber tubing.;Using this flow system, we evaluated the automated peak-frequency tracing algorithm used on an ATL HDI Doppler instrument. Values of diagnostic indices, including maximum systolic, minimum diastolic, time-averaged peak-frequencies, and pulsatility and resistance indices, measured by the automated routine were found to agree to within 4.5% of those measured manually.;The second approach was to develop a phantom which uses an acoustic beam splitter to combine separate clutter and flow sources to form the Doppler signal. The flow component is provided either by a second belt (dual-belt phantom) or by a vascular phantom (belt/vascular phantom). The acoustic beam splitter splits the ultrasonic beam so that the same Doppler sample volume is within the clutter belt and flow source.;We evaluated the effects of the clutter belt velocity, flow belt velocity, and clutter-to-flow power ratio on the reported colour Doppler shifts. The results show that the choice of wall filter, as well as the amplitudes and velocities of the clutter and flow components, affect the measured Doppler shift. Results obtained with the belt/vascular phantom show that colour Doppler shifts due to the moving fluid depend strongly on the clutter belt velocity and choice of wall filter. However, only a small dependence on Doppler signal strength was observed.
Rickey, Daniel William, "Evaluation Of Doppler Ultrasound Velocity And Flow Measurements" (1995). Digitized Theses. 2572.
The text passage describes the evaluation of Doppler ultrasound measurements of blood flow using a flow system and a phantom with an acoustic beam splitter. It includes specific measurements and comparisons of diagnostic indices and the effects of various parameters on Doppler shifts.
no_question
Given a text passage, determine:
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    2. If an answer to that mathematical question is provided in the text

First, describe the content structure you found in 1-2 sentences.

Then provide your analysis in the following format:
TYPE: <one of the following values>
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- SINGLE_QUESTION
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- MULTIPLE_QUESTIONS
- MULTIPLE_QUESTIONS_WITH_ANSWERS
system
Date of Award
Doctor of Philosophy
Doppler ultrasound instruments have been used clinically for about 30 years and have proved to be highly reliable for the detection of arterial disease. In addition, a number of different Doppler instrument designs and techniques have been proposed to provide quantitative measurements such as volume blood flow, percent stenosis, and waveform indices. Before any measurement technique can be used, it must be validated.;We chose a two-pronged approach to the problem of evaluating Doppler ultrasound measurements of blood flow. We first developed a flow system that mimics the vasculature. The flow system comprises a computer-controlled pump, blood mimic, and a wall-less vessel phantom. A computer-controlled pump allows the production of accurate constant flow as well as pulsatile flow waveforms. The wall-less vessel phantom eliminates the artefacts introduced by the high attenuation and impedance mismatches of common vessel mimics such as latex rubber tubing.;Using this flow system, we evaluated the automated peak-frequency tracing algorithm used on an ATL HDI Doppler instrument. Values of diagnostic indices, including maximum systolic, minimum diastolic, time-averaged peak-frequencies, and pulsatility and resistance indices, measured by the automated routine were found to agree to within 4.5% of those measured manually.;The second approach was to develop a phantom which uses an acoustic beam splitter to combine separate clutter and flow sources to form the Doppler signal. The flow component is provided either by a second belt (dual-belt phantom) or by a vascular phantom (belt/vascular phantom). The acoustic beam splitter splits the ultrasonic beam so that the same Doppler sample volume is within the clutter belt and flow source.;We evaluated the effects of the clutter belt velocity, flow belt velocity, and clutter-to-flow power ratio on the reported colour Doppler shifts. The results show that the choice of wall filter, as well as the amplitudes and velocities of the clutter and flow components, affect the measured Doppler shift. Results obtained with the belt/vascular phantom show that colour Doppler shifts due to the moving fluid depend strongly on the clutter belt velocity and choice of wall filter. However, only a small dependence on Doppler signal strength was observed.
Rickey, Daniel William, "Evaluation Of Doppler Ultrasound Velocity And Flow Measurements" (1995). Digitized Theses. 2572.
user
The text passage describes the evaluation of Doppler ultrasound measurements of blood flow using a flow system and a phantom with an acoustic beam splitter. It includes specific measurements and comparisons of diagnostic indices and the effects of various parameters on Doppler shifts.

TYPE: NO_QUESTION