Localization and quantification of magnetic nanoparticles by multichannel magnetorelaxometry for in vivo hyperthermia studies in carcinoma models

Abstract

In magnetic fluid hyperthermia / thermal ablation (MFH), superparamagnetic iron oxide nanoparticles (MNP) exposed to an externally applied alternating magnetic field generate heat specifically in the tumor region, which inactivates cancer cells with minimal side-effects to the normal tissue. The quantity of MNP needs to be thoroughly controlled to govern adequate heat production in the carcinoma region. We demonstrate the capability of magnetorelaxometry (MRX) for the non-invasive quantification and localization of MNP accumulation in small animal models. The results of our advanced MRX measurements using a 304-multichannel bio-magnetic SQUID system on two mice hosting two different carcinoma models (9L/lacZ, MD-AMB-435) are presented. The position and magnitude of the magnetic moment is reconstructed from the measured spatial magnetic field distribution by a magnetic dipole model fit applying a Levenberg-Marquadt algorithm. Therewith, the center of mass of the MNP accumulation in the tumor region of the mouse and moreover the amount of MNP in the determined region is quantified. This study shows that magnetorelaxometry is well suited for in vivo monitoring of MNP accumulation in hyperthermia application during cancer therapy. © 2009 Springer-Verlag.