Characterisation of adherent microbubbles for molecular targeted ultrasound

Abstract

Molecular imaging is a field of medicine which can offer great potential for both diagnostic and therapeutic purposes. Within this field contrast enhanced ultrasound displays the possibility of making molecular imaging a cost effective viable tool in an increasingly diverse set of clinical situations. One of the current challenges associated with this technique is how one differentiates the signal for adherent microbubbles from those produced by the bulk non-adherent population. The first part of this thesis acoustically examines the response of single microbubbles under the effects of adhesion and compares the response observed with that of the MBs non-adherent counterpart. It was found experimentally that differences could be observed in both the 2nd harmonic signals generation and in the stability over repeated exposure. These differences could be utilised as the basis for discretisation imaging strategies. The second section of this thesis attempts to characterize these differences in terms of current theoretical models. A more comprehensive modelling strategy is utilised for the fitting of increasingly complex theoretical models. Good agreement was found with the outputs of this fitting procedure with previously reported parameters. Further detail could also be observed in the form of various size/resonance effects which have not previously been reported. There was little observed difference between the parameters extracted for the adherent and non-adherent MBs although it was suggested that the effective elasticity of an adherent MB could be elevated in comparison to its non-adherent counterpart in the region of resonance. Efforts will be required to control and account for some of the variability observed in MB response before this can be stated definitively however.