Ultrasound is a very attractive and patient-friendly imaging technique, as it is easy to use, fast and non-invasive. Nevertheless, its use is severely limited by the low stability of current contrast agents, as they contain gaseous or vaporizing phase. We developed perfluorocarbon-loaded poly(lactide-co-glycolide) nanoparticles (NPs), which are suitable for long-term imaging, in a time-scale of days. However, the mechanism of contrast generation is completely unclear. The internal structure of our NPs appears completely different from currently reported perfluorocarbon-loaded colloids. Thus, elucidating the internal structure of these nanoparticles is a key to describe the mechanism of acoustic contrast generation. As SANS has been successfully applied by other researchers to study fluorinated colloids, we propose SANS to investigate the structure of our NPs.