Contrast agents are often used in medical imaging and more specifically in x-ray based imaging techniques to enhance image contrast, therefore improve quality of diagnosis. A good contrast media must have the highest attenuation coefficient (radiopacity), among other criteria. Polymers can be made radiopaque by blending them with heavy metals (good radio-opacifying agents due to their high atomic number). A cause of trouble is the leakage of heavy metals into the body. In order to avoid this issue, the contrast agent should be attached to the polymer material. The purpose of this study is to develop iodinated polymer nanoparticles which will be used as contrast agents for tomography using a Spectral Photon Counting Computed Tomography (SPCCT Scanner).

 The iodinated polymer was prepared by covalently linking an iodinated molecule onto Poly(vinyl alcohol). The radiopaque moieties were successfully incorporated onto the polymer and the grafting ratio, calculated by 1H NMR, is over 50%. Nanoparticles of iodinated polymers were prepared using the Nano-precipitation method. Particle size was measured by Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM); stability was assessed over time. Radio-opacity of the contrast media was evaluated in-vitro on phantoms prepared with suspensions of contrast agents at different concentrations and in-vivo by experiments performed on small animals (intravenous injections to rabbits). X-ray absorption were measured on a conventional CT and on the SPCCT.

 The objective is to assess the benefits of the spectral scanner in comparison to a standard CT. It is expected that the photon counting detector of the SPCCT will improve the signal-to-noise ratio. Since the K-edge of iodine is too low, those iodinated nanoparticles will be loaded with other heavy metals in order to allow specific observation at the K-edge of the heavy atoms, in the future.