The Synergy of Magnetic Particle Imaging and Magnetic Nanoparticle based Thermal Therapies

Abstract: Magnetic nanoparticle (MNP) based thermal therapies, such as magnetic fluid hyperthermia, utilizes a fluid suspension of biocompatible superparamagnetic iron oxide nanoparticles administered systemically or locally to the target diseased region. When magnetically excited by an externally applied alternating magnetic field, these nanoparticles act as local heat sources. While this method has the potential for highly-localized therapy in a relatively non-invasive manner, several challenges remain for this method of hyperthermia. One difficulty is dose planning due to the lack of quantitative non-invasive methods to evaluate local accumulation of nanoparticles. Another challenge is the low accuracy of the excitation magnetic field which results in accidental heating of nanoparticles that non-specifically accumulate in off-target regions. In this review, we introduce a new imaging technique called Magnetic Particle Imaging (MPI), which provides new functionalities to address these challenges. MPI’s nanoparticle signal is independent of surrounding tissue heterogeneity, enabling fully quantitative imaging of the nanoparticle accumulation at the target diseased region for robust dose planning. In addition, the scanner’s gradient field can be shaped to generate a field-free-point focal spot which has been shown to increase excitation accuracy and achieve millimeter-scale heating at-depth. Taken together, Magnetic Particle Imaging has strong synergy with MNP-based thermal therapies and has the potential to become a powerful platform for image-guided, dose-accurate thermal nanomedicine.