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978-3-86853-917-2, Reihe Medizintechnik
Acoustic Analysis of Ultrasound Contrast Agents
187 Seiten, Dissertation Ruhr-Universität Bochum (2011), Softcover, A5
Ultrasound Contrast Agents consist of microbubbles with diameters in the micron range. When insonified with diagnostic ultrasound, these microbubbles oscillate nonlinearly. Using suitable pulse sequences, signals originating from microbubbles can be distinguished from signals originating from tissue scatterers. Furthermore, by increasing the insonification pressure, contrast agents can be destroyed locally, potentially enabling applications in targeted drug delivery.
In this thesis, the acoustical properties of ultrasound contrast agents for destructive and non-destructive imaging were considered. A theoretical model for microbubble destruction was developed. Using an experimental set-up, the model was be validated for microbubbles of varying chemical composition.
Detection schemes for microbubbles employ pulsing sequences to detect signals originating from microbubbles. These pulsing sequences are developed from heuristic assumptions on microbubble oscillation. To enable a systematic analysis of the potential of novel imaging methods, nonlinear system theory in the form of Volterra series was employed to develop a model for diagnostic ultrasound imaging. Models for the two main sources of nonlinearity, nonlinear sound propagation and nonlinear microbubble oscillation were identified. The development of this model enabled the development of imaging modes with substantially increased image contrast.