Characterisation of functionalised microbubbles for ultrasound imaging and therapy

Abstract

Functionalised microbubbles have shown considerable potential both as contrast agents for ultrasound imaging and as a means of enhancing ultrasound mediated therapy. With the development of advanced techniques such as quantitative ultrasound imaging and targeted drug delivery, the accurate prediction of their response to ultrasound excitation is becoming increasingly important. Characterising microbubble behavior represents a considerable technical challenge on account of their small size (<10 μm diameter) and the ultrasound frequencies used to drive them in clinical applications (typically between 0.5 and 20 MHz). This chapter examines the three main techniques used for the characterization of microbubble dynamics: Ultra-high speed video microscopy, laser scattering and acoustic attenuation and back scattering measurements. The principles of the techniques are introduced with examples of their applications and their relative advantages and disadvantages are then discussed. In the second half of the chapter magnetically functionalized microbubbles are used as a case study and results obtained using each of the three techniques are presented and compared. The chapter concludes with recommendations for combining different methods for microbubble characterization.