Comparative Assessment of the MRI Enhancement Power of Novel Nanosystems Through Theoretical Simulations

Multimodal contrast agents (CAs) allow the enhancement of medical images acquired through different techniques by employing a single contrast injection, with significant benefits for diagnostic outcome. The present study is focused on the characterization of the magnetic behavior of a novel CA class, consisting of silica (Si) nanoparticles (NPs) covered by either superparamagnetic iron oxide (SPIO) NPs or FePt-IO nanocrystals and designed to be detected through both ultrasound and magnetic resonance imaging (MRI). The use multimodal nanoparticles as negative MRI contrast agents could open up new perspectives for the development of novel tools for nanomedicine, combining different non-ionizing techniques for targeted imaging of specific diseased cells. In this work, we simulated the MRI signal of a blood vessel in presence of the new bimodal CAs and compared it with the response of the superparamagnetic NPs alone. The performed numerical simulations showed that the magnetic response of the novel nanocomposites, in terms of signal magnitude, was similar to that of the conventional superparamagnetic NPs for values of echo time (TE) shorter than 0.4 ms, while for longer TEvalues it was even better, showing a stronger vessel enhancement leading to an easier detection of the smaller vessels. Therefore, the tested bimodal NPs have the potential for an effective employment as MRI CAs.