First Investigation of Gadolinium-Based Nanoparticles for Radiosensitization and Enhanced Imaging on the Australian MRI-linac

High atomic number nanoparticles have the capacity to boost the therapeutic efficacy of radiotherapy by enhancing tumor-localized radiation damage. AGuIX® is a gadolinium-based nanoparticle that has been shown to increase survival times compared to radiotherapy alone in pre-clinical animal studies. In addition to its high atomic number, gadolinium also provides strong positive contrast in magnetic resonance imaging (MRI) and is able to cross the blood-brain barrier where disrupted by a tumor. Here we report on the progress of the first study of AGuIX® using an integrated linear accelerator (linac) and MRI scanner. The Australian MRI-Linac is a dedicated research facility combining a linear accelerator for delivery of therapeutic radiation with a custom-designed 1 T magnet, allowing MR images to be acquired during treatment. This work demonstrates the imaging and irradiation capability of the Australian MRIlinac on a rat brain tumor model to extend studies that were previously performed with separate MRI and radiotherapy. The MRI contrast provided by AGuIX® not only aids delineation of the tumor target for verification and/or adaptation of the treatment plan, but can also monitor the uptake of gadolinium in the tumor to optimize the treatment delivery time to achieve radio-therapeutic gain from radio-enhancement effects. This work paves the way for a clinical trial of AGuIX® in Australia.