Acoustic Droplet Vaporization : An Assessment of How Ultrasound Wave Parameters Influence the Vaporization Efficiency

University essay from KTH/Medicinteknik och hälsosystem

Abstract: Acoustic droplet vaporization (ADV) is a process in which a phase shift of a liquified droplet into a gaseous microbubble, is triggered using an ultrasonic wave. In contrast to utilizing conventional contrast agents in ultrasound, the phase change contrast agents used in ADV can extravasate into tumor tissue, and they offer a greater circulatory lifespan, thereby increasing the potential applications in which they can be utilized. In this project, the impact of different ultrasound parameters on the efficiency of ADV was investigated, using a programmable ultrasound system. Two different ultrasound sequences were designed, for imaging and vaporization of droplets. Furthermore, three different sets of experiments were performed. Firstly, the vaporization effect of different imaging voltages was investigated, whereby a setting of 15V was identified as an able voltage for the remaining experiments. Secondly, experiments concerning the effect of vaporizing frequency on the ADV efficiency were performed, including the use of single and dual frequencies. Lastly, different frequency settings were combined with varying the number of cycles, to assess how the choice of pulse length influences the vaporization. The results from the project indicate that no substantial difference in ADV efficiency is achieved when using different frequency settings for perfluoropentane droplets encapsulated by cellulose nanofibers. However, the results provide clear indications of the benefit of using longer pulse durations on the vaporization efficiency. In conclusion, further studies are required before ADV can be translated into a clinical setting.

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