Ultraharmonic Imaging of Polymer-shelled Microbubbles

University essay from KTH/Skolan för kemi, bioteknologi och hälsa (CBH)

Abstract: Ultrasound has been established as one of the most widely used imaging modalities for diagnostic purposes, due to the several advantages it provides in comparison with other techniques. Hence, ways to further improve the confidence in diagnoses provided by ultrasound are constantly being investigated. One of them is the introduction of Ultrasound Contrast Agents, which can enhance the weak echoes produced by the small vessels, improving the imaging performance. In this study, a setup was created and six ultrasound imaging techniques were implemented by using the Verasonics Research System®, in order to take advantage of the different behavior between the tissue and the Polyvinyl-Alcohol microbubbles, when exposed to ultrasound. These were: Fundamental B-mode, Ultraharmonic, PulseInversion, Subharmonic Pulse Inversion, Ultraharmonic Pulse Inversion, Combination of the Sub- and Ultraharmonic Pulse Inversion. For the assessment of the bubbles’ response, the amplitude spectra were used, which showed a limited detection around the ultraharmonic region. For the evaluation of the imaging performance of the techniques, the Contrast-to-Tissue (CTR) and Contrast-to-Noise Ratios (CNR) were calculated. The Combination of the Sub- and Ultraharmonic Pulse Inversion reported the highest imaging performance among all the techniques. A comparison with previous articles provided a similar pattern in terms of CTR.

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