AbstractSuperparamagnetic iron oxide nanoparticles (SPIONs) are used in many biomedical applications such as drug delivery, as therapeutic agent for hyperthermia treatment and contrast agent for molecular magnetic resonance imaging (MRI). Apart from the synthesis of novel SPIONs there have been technical developments such as new MRI pulse sequences for positive contrast imaging. The most prominent are GRadient-echo Acquisition for Superparamagnetic particles with Positive contrast (GRASP), Inversion Recovery with ON-resonant water suppression (IRON) and Susceptibility Gradient Mapping (SGM).
Four novel SPIONs of different sizes, coatings and surface charges were assessed in terms of their application as MR contrast agents. The !" and !" ∗ relaxivities in water and breast cancer cells were investigated in vitro and the effects on the relaxivity when SPIONs move from a free to a bound state were described. The most promising SPION was also investigated in vivo with a multi echo gradient-echo sequence and a range of positive contrast imaging techniques. For the GRASP and IRON technique a dynamic preparation phase was devised to optimise the positive contrast imaging parameters. We developed a novel positive contrast imaging technique based on the Dixon multi echo sequence for improved SPION visualisation and quantification. The Dixon positive contrast technique was compared to already established techniques such as GRASP, IRON and SGM. Finally, it was determined that fat suppression with Dixon is superior to SPIR for positive contrast imaging with the IRON technique.
Overall, this work makes a contribution to the development of novel SPIONs for nanotheranostic applications. In particular, new developments for positive contrast imaging with SPIONs are presented that could further improve the usability of these techniques in future diagnostic applications.
|Date of Award
|Tobias Schaeffter (Supervisor) & Rene Botnar (Supervisor)