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Title: In-vitro quantitative assessment of ultrasonic contrast agents
Author: Sboros, Vassilis
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2000
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The agents Levovist, QuantisonTM, MyomapTM, and DMP115 were used in the various investigations. The experiments were based on acquiring the ultrasonic echoes created by the agents in water suspensions. Radiofrequency echo data frames were collected with an ATL Ultramark 9 Scanner (UM9). The normalised mean backscatter intensity of a region of interest in the image was calculated and formed the basis of the quantitative analysis. Normalisation was carried out using tissue or blood mimicking material as the reference target. Levovist displayed a diminished backscatter when introduced into degassed water. An extended stability study varying also the acoustic pressure showed that QuantisonTM and MyomapTM exhibited accelerated decay at higher acoustic pressures in a degassed environment. The backscatter properties changed with time and varied amongst agents in continuous imaging, and the feasibility of quantitative measurements using this imaging approach was fully explored in-vitro. A newly defined physical quantity called Overall Backscatter that equals the integral of the decay of the normalised backscatter intensity over time, showed that it could optimally describe the properties of the agents in in-vitro imaging. A new imaging approach had to be implemented in order to isolate the scattering properties of the contrast agent from its destruction process. To achieve this, individual scan sweeps were performed at defined intervals. The normalised backscatter of the agents was modelled as a function of the bubble concentration and the peak negative pressure. Using very low concentrations, individual bubbles were studied, and it was found that contrast agents scatter proportionally to the 3rd order of acoustic pressure. The results also suggested that above 0.6MPa peak negative pressure, free bubbles were formed for QuantisonTM and DMP115. Further work using an advanced version of the system assessed the optimal setting for imaging DMP115 in-vitro.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available