1E-2 Experimental Characterization of Ferucarbotran (Resovist ®) as a Photoacoustic Nanoparticle Contrast Agent

Photoacoustics (PA) combines the high contrast of optical imaging modalities with the high resolution of clinical ultrasound. Photoacoustic contrast agents improve the maximum imaging depth of photoacoustic imaging and may render it possible to use this modality for molecular imaging. Organic dyes, like indocyanine green, or inorganic nanoparticles are used as photoacoustic contrast agents. However, the toxicological properties of many nanoparticles, like gold, have still not been fully investigated. Therefore, in this paper the photoacoustic properties of Ferucarbotran are investigated. Ferucarbotran is a clinically established contrast agent for magnetic resonance imaging. It consists of superparamagnetic iron oxide nanoparticle cores coated with carboxydextran. In order to evaluate the photoacoustic application of Ferucarbotran, gelatin phantoms with different Ferucarbotran concentrations were fabricated. These phantoms, which were mounted on a three-dimensional positioning system, were irradiated by a Nd:YAG laser (1064 nm) and the photoacoustic signals were acquired by a single element ultrasound transducer (7.5 MHz). The experiments showed that in order to achieve a 6 dB gain of photoacoustic received signal energy compared to signals from gelatin a Ferucarbotran concentration of 1.9 mumol Fe/ml is needed. This concentration is equivalent to the quadruple in vivo concentration of Ferucarbotran in the human liver