Imaging tracers for cell tracking applications with magnetic resonance imaging (MRI) and positron emission tomography (PET)

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A growing number of emerging medical diagnostics and therapeutic procedures require the tracking of cells in vivo. In order to monitor and to quantify the fate of cells used in novel procedures for gene therapies, for Langerhans islet implantation (to cure diabetes), or for stem cell therapeutic approaches, it is necessary to use magnetic resonance imaging (MRI). MRI is now very well implanted in a majority of mid- and large-scale medical facilities. It is accessible and provides images of anatomical resolution without the use of ionising radiation. In order to visualise cells in vivo, the cells must be labelled with magnetic imaging probes made of the elements Fe, Gd, or Mn. These tracers either "enhance" or "decrease" the MRI signal to reveal the presence of labelled cells. In this research proposal, new Gd2O3 and MnO will be developed that will enable more quantitative, higher resolution cell tracking studies. Innovative nanoparticle surface treatments will be developed to prevent the degradation of particles submitted to harsh fluid environments. Then, to more precisely and more finely define the presence of small amounts of labelled cells, and to enhance the quantitative aspects of whole-body cell tracking, magnetic and radioactive nanoparticles will be developed. For this purpose, positron emitters (radioisotopes) will be used to "dope" or to "label" magnetic nanoparticles. Of all whole-body imaging modalities, positron emission tomography allows for the highest detection sensitivity. With the recent commercialization of dual PET/MRI scanners, which enable the coupling of high-resolution MRI with high-sensitivity PET, the new "PET/MRI" tracers developed in this research proposal will allow for more quantitative cell tracking studies. Finally, one aspect of the research program proposal addresses the development of a PET/MRI tracer synthesizer, a small equipment that may be advantageously installed directly in clinics and laboratories.