SMART RHESINs for magnetic particle imaging: impact of viscosity-independent relaxation on image reconstruction

Magnetic particle imaging (MPI) is a promising medical imaging modality that leverages the magnetic properties of nanoparticles. Traditionally, MPI tracers have been limited to commercially available nanoparticles, but specialized tracers could improve signal detection and expand applications. Here, we introduce SMART RHESINs, an innovative tracer design for MPI. In SMART RHESINs, synomag®-D nanoparticles are encapsulated in hollow nanospheres, shielding them from external influences like viscosity changes and enabling signal quantification independent of the surrounding medium. We demonstrated that the phase angle obtained through MPS is a rapid, predictive metric for assessing tracer suitability for MPI applications. Unlike the system matrix from non-encapsulated synomag®-D, the system matrix from aqueous synomag®-D-encapsulated SMART RHESINs allowed reconstructing immobilized SMART RHESINs, underscoring design robustness. SMART RHESINs hold potential for quantitative measurements across diverse environments, broadening the scope of MPS and MPI as a versatile tracer platform for quantitative imaging.