In Vivo and Ex vivo experimental MPI angiography with high selection field strength and tailored SPIO nanoparticles

MPI shows great promise for safe angiography, blood pool, and perfusion imaging. MPI images have unprecedented contrast that enables unambiguous measurements of tracer quantity and location [1-4]. At present, pre-clinical MPI resolution does not compare with pre-clinical MRI and CT, which routinely achieve better than 100-micron resolution. MPI's low resolution is primarily due to limitations in MPI hardware and magnetic nanoparticles. To begin to close this resolution gap, we are developing higher-field MPI gradients [3] and specialized MPI magnetic nanoparticles [4]. Since MPI resolution improves with stronger selection field gradients, we recently completed construction of a high-field MPI imager with a 7 T/m × 3.5 T/m × 3.5 T/m magnetic field gradient. Further, magnetic nanoparticles developed specifically for MPI show dramatic improvements in resolution and SNR over commercially available nanoparticles such as Resovist (BayerSchering) [4]. In this work, we demonstrate that combining these two breakthroughs enable improvements in MPI angiography images that begin to close the gap between MPI and pre-clinical MRI and CT.