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Subharmonic Imaging of Polymer-Shelled Contrast Agents
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
2018 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesisAlternative title
Subharmonisk avbildning av polymera kontrastmedel (Swedish)
Abstract [en]

The harmonic generation due to the nonlinear behavior of Ultrasound Contrast Agents (UCAs) must be exploited for improved efficiency when imaging vascular targets in the neighborhood of highly echogenic tissue. One may even further improve the efficiency by focusing on the subharmonic generation of the UCAs, which is an even more exclusive property than the generation of higher harmonics, for improved Contrast-to-Tissue ratio (CTR). The aim of this work was first, the design of a set-up for nonlinear imaging of Poly-Vinyl Alcohol (PVA) based UCAs on The Verasonics Research System with special focus on nondestructive Subharmonic Imaging. The second part of the work addressed the evaluation of the subharmonic response provided by the agents in the developed setup. Six different imaging techniques were developed. These were Fundamental B-mode imaging (FB), Pulse Inversion imaging (PI), and a Contrast Pulse Sequence based on three pulses (CPS3), with and without a focus on the subharmonic component by the implementation of a Linear Bandpass Filter (LBF). Experiments were performed on a tissue mimicking flow phantom and the performance of the agents for each technique was determined in terms of CTR and CNR. The PVA agents provided a backscattering enhancement of the order of 23 dB through FB imaging. However, the performance of the FB technique was unsatisfactory in terms of CTR. The CPS3 sequence performed best of the six techniques with an improvement of 14 dB and 13 dB in CTR and CNR, respectively, compared with the FB technique. Combining the LBF around the subharmonic component with the multi-pulse techniques of PI and CPS3 resulted in a degraded CTR performance due to significant amount of signals from tissue around the subharmonic component and insufficient subharmonic detection from the PVA agents. 

Place, publisher, year, edition, pages
2018. , p. 40
Series
TRITA-CBH-GRU ; 2018:68
Keywords [en]
Ultrasound Imaging, Contrast Enhanced Ultrasound Imaging, Contrast Agents, PVA Contrast Agents
National Category
Medical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-233492OAI: oai:DiVA.org:kth-233492DiVA, id: diva2:1240283
Subject / course
Medical Engineering
Educational program
Master of Science - Medical Engineering
Presentation
2018-06-07, Stockholm, 20:35 (English)
Supervisors
Examiners
Available from: 2018-08-21 Created: 2018-08-20 Last updated: 2022-06-26Bibliographically approved

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