Hepasphere TM behavior during venous drainage simulation at 1 . 5 T *

Stability of the magnetic resonance (MR) contrast agent inside vascular occlusion agents is important for their localization with magnetic resonance imaging (MRI). The aim of this paper is to study the behaviour of the superparamagnetic iron oxide (SPIO) within Hepaspheres microparticles (MP) by MRI when they are submitted to negative pressure induced by venous drainage of a tumor. Therefore, a venous drainage model was established and three parameters were taken into account according to physiologic parameters in tumors: pH, temperature and flow blood rate. Four cycles of pumping were performed with the presence of labeled Hepaspheres with Endorem. Several MR images of MP and perfusion liquid were taken before and after pumping. Endorem release was determined after correction of non-uniformity intensities in MR images. Intensity variation according to spatial position, coil and MR acquisition parameters was studied. Labeled microparticles (LB*MP) appeared as black spots in MRI images whatever duration and pH. Our model demonstrates the stability of the SPIO inside the occlusion agent during time. Moreover, the proposed correction method proves the reduction of the intensity non-uniformity in MRI images.