Acoustic characterization of a new trisacryl contrast agent. Part II: Flow phantom study and in vivo quantification.

The biocompatible trisacryl particles (TMP) are made of a cross-linked acrylic copolymer. Their inherent acoustic properties, studied for a contrast agent application, have been previously demonstrated in a in vitro Couette device. To measure their acoustic behaviour under circulating blood conditions, the TMP backscatter enhancement was further evaluated on a home-made flow phantom at different TMP doses (0.12–15.6mg/ml) suspended in aqueous and blood media, and in nude mice (aorta and B16 grafted melanoma). Integrated backscatter (IB) was measured by spectral analysis of the Doppler signals recorded from an ultrasound system (Aplio®) combined with a 12-MHz probe. Doppler phantom experiments revealed a maximal IB of 17±0.88dB and 7.5±0.7dB in aqueous and blood media, respectively. IB measured on mice aorta, in pulsed Doppler mode, confirmed a constant maximal value of 7.29±1.72dB over the first minutes after injection of a 7.8mg/ml TMP suspension. Following the injection, a 60% enhancement of intratumoral vascularization detection was observed in power Doppler mode. A preliminary histological study revealed inert presence of some TMP in lungs 8 and 16 days after injection.