University of Twente Student Theses


The effect of ambient pressure on the subharmonic acoustic response of monodisperse microbubbles

Schroer, W. (2022) The effect of ambient pressure on the subharmonic acoustic response of monodisperse microbubbles.

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Abstract:In this thesis, the effect of the ambient pressure on the acoustic response of three different kinds of monodisperse microbubbles, with different phospholipid shell stiffness was studied. The shell stiffness was modified by adding different molar fractions of palmatic acid to the shell. Using a Verasonics Vantage research ultrasound system and the P4-1 ultrasound probe, both the fundamental and subharmonic mean power of the scattered bubble signal during an ambient pressure increase was investigated. A new variable, the Corrected Change of Subharmonic (CCoS) is introduced to combine both the fundamental and subharmonic scattered behaviour of the bubbles into a single variable in order to make hydrostatic pressure estimations of the medium surrounding the bubbles. The results show that increasing the stiffness of the shell of lipid coated microbubbles significantly increases measured values of the CCoS. This increase is caused by both the changed attenuation spectra of the bubbles at low acoustic pressures, as well as the change in acoustic response of the bubbles due to increasing stiffness. The resolution of the hydrostatic pressure estimation is still insufficient for clinical applications, but the method shows promising results and, in the future, might be a clinically viable alternative to current methods.
Item Type:Essay (Master)
Faculty:TNW: Science and Technology
Subject:33 physics, 44 medicine
Programme:Biomedical Engineering MSc (66226)
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