title: Magnetic resonance and ultrasound contrast imaging of polymer-shelled microbubbles loaded with iron oxide nanoparticles.
abstract: Dual-mode contrast agents (CAs) have great potential for improving diagnostics. However, the effectiveness of CAs is strictly related to both the solution adopted to merge the two agents into a single probe unit, and the ratio between the two agents. In this study, two dual-mode CAs for simultaneous magnetic resonance imaging (MRI) and ultrasound imaging (UI) were assessed. For this purpose, different densities of superparamagnetic iron oxide nanoparticles (SPIONs) were anchored to the external surface of polymer-shelled microbubbles (MBs) or were physically entrapped into the shell.In vitrostatic and dynamic experiments were carried out with a limited concentration of modified MBs (106bubbles ml-1) by avoiding destruction during UI (performed at a peak pressure lower than 320 kPa) and by using a low-field MRI system (with a magnetic flux density equal to 0.25 T). Under these conditions, different imaging techniques, set-up parameters and SPION densities were used to achieve satisfactory detection of the CAs by using both UI and MRI. However, when the SPION density was increased, the MRI contrast improved, whereas the UI contrast worsened due to the reduced elasticity of the MB shell. For both UI and MRI, MBs with externally anchored SPIONs provided better performance than MBs with SPIONs entrapped into the shell. In particular, a SPION density of 29% with respect to the mass of the MBs was successfully tested.
authors.affiliation: Department of Electrical, Electronic, Telecommunications Engineering, and Naval Architecture , University of Genoa , Genoa , Italy.
authors.forename: Claudia
authors.initials: C
authors.lastname: Sciallero
authors.affiliation: Esaote S.p.A. , Genoa , Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Balbi
authors.affiliation: Department of Chemistry , University of Rome Tor Vergata , Roma , Italy.
authors.forename: Gaio
authors.initials: G
authors.lastname: Paradossi
authors.affiliation: Department of Electrical, Electronic, Telecommunications Engineering, and Naval Architecture, University of Genoa, Genoa, Italy; Pattern Analysis and Computer Vision, Istituto Italiano di Tecnologia, Genoa, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Trucco
keywords: dual-mode contrast agents; magnetic resonance imaging; medical ultrasound; polymeric microbubbles; superparamagnetic iron oxide nanoparticles