Metal colloids showing high signal and enhanced contrast in cellular and molecular imaging with MRI and PET/MRI

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Molecular imaging allows modern medicine to examine the functions of molecules and cells in living organisms. Diseases such as cancer, atherosclerosis and Alzheimer, can now be detected precisely and non-invasively at a much earlier stage. Imaging scanners have reached a high level of development and henceforth intense efforts are being invested in the development of biomarkers with improved properties. This research program addresses a crucial aspect of molecular imaging: the development of contrast agents and tracers (biomarkers) providing high and specific signal in magnetic resonance imaging (MRI) and positron emission tomography (PET). In fact, a next generation of scanners combining MRI and PET will soon become a reality in the clinic. MRI is a non-invasive imaging technique providing high resolution pictures in low density tissues. Magnetic molecules or nanoparticles are often necessary to finely delineate the vasculature, to precisely identify disease artefacts, and to track cells. The rather poor sensibility per unit of biomarker is the major limitation of MRI, which requires the use of large amounts of magnetic metals in-vivo. PET is also a non-invasive imaging technique, based on the detection of radioactive tracers at very high sensitivity. This method requires very small quantities of radioactive atoms; the resolution however remains lower than with MRI. At present, both imaging techniques (MRI and PET) can be used separately for studying physiological features and molecular targets. Could we perform both MRI and PET at the same time? Magnetic metal colloids in the form of nanoparticles, can be used to improve the specificity of the MRI signal. By doping these crystalline "nanomaterials" with carefully selected radioactive atoms, a next generation of biomarkers could become available for dual PET/MRI procedures. This research program focuses on the synthesis, characterization and signal study of dual contrast agents produced in the form of magnetoradioactive colloids. In the long term, such colloids could be used as molecular tags, as cell markers, and also as enhancers of MRI contrast for biomedical devices.