| To date, few contrast agents have been used for imaging studies across different modalities. There are no contrast agents available commercially, and few for research purposes, that have been developed to specifically optimize multi-modal image analysis utilizing US, MR, and CT technology. The overall objective of the studies detailed in this dissertation is to investigate a prototype contrast agent that provides optimal image enhancement for MRI (allowing, for example, high longitudinal relaxation rate relaxivity at high or very high magnetic field strength), CT (enhancing X-ray attenuation at conventional CT scanning energies), and US imaging (improving re-radiation effects such as backscatter). An important attribute of such a prototype multi-modal contrast agent should include ease of modification for molecular targeting. In addition, this agent should provide the means to couple therapeutic intervention with diagnostic imaging. Relevant examples include the encapsulation of genes and/or drugs for target specific delivery or even the utilization of the intrinsic properties of the contrast agent for therapy (for example, via gadolinium neutron capture therapy in the case of gadolinium-containing biopharmaceuticals).;Towards this aim experimental studies will be presented for the biophysical characterization of gadolinium oxide particulate contrast agents as a novel class of prototype multi-modality contrast agent. In chapter 2 an analysis of the MR contrast enhancement and X-ray attenuation properties of small particulate gadolinium oxide and gadolinium oxide albumin microspheres for MR and CT imaging is presented. MR relaxometry and nuclear magnetic relaxation dispersion (NMRD) characterization of the water-proton relaxation properties of small particulate gadolinium oxide and gadolinium oxide albumin microspheres is provided in chapter 3. In chapter 4 the structure and magnetic properties of dextran small particulate gadolinium oxide nanoparticles are explored in order to provide insight into their potential use as high magnetic field strength MR contrast agents and to elucidate their potential for improvement of SPGO water-proton relaxation. In chapter 5, speed of sound, attenuation, backscatter and video density studies are presented to characterize the acoustic properties of gadolinium oxide albumin microspheres (paramagnetic polymerized protein microspheres) for use as a contrast enhancing agent in US imaging. |
