In this study the acoustic characterisation of ultrasound contrast agents (UCA) for subharmonic imaging (SHI) using an Aixplorer (Supersonic Imagine, France) scanner was investigated. Dynamic contrast enhanced ultrasound (DCE-US) is a non-invasive imaging method providing a means of imaging the microvasculature. UCAs are currently used clinically for qualitative purposes, however, they are not currently used quantitatively. UCAs produce subharmonic signals at half of the transmitted fundamental frequency when insonated with ultrasound energy, whereas native tissue does not, and hence SHI offers the potential to image the microvasculature with better sensitivity and also with improved accuracy for use in quantitative measurements. UCAs were characterised in Perspex test cells containing acoustic windows using a single element transducer (V306, Olympus, USA) including: characterisation of size, attenuation and linearity of the signal with concentration of the UCA. A processing protocol using the Welch transform was developed to process raw radio frequency data from the scanner, along with hydrophone experiments investigating the frequency spectrum output and peak negative pressure of the SC6-1 probe. The characterisation of the signal from native bubble populations will be presented along with a developed protocol to modify the size distribution of the UCAs to establish the optimum bubble distribution for SHI. A robust method for handling the raw radiofrequency data will be presented. The results of this investigation will allow for the development of an optimised protocol for the acquisition of subharmonic signals using the Aixplorer system which could be used in a clinical setting. Supported by the Irish Research Council, Government of Ireland Postgraduate Scholarship and IAPM Young Investigator Grant