Extended-linear polymeric contrast agents, and synthesizing methods, for medical imaging

This invention relates to nuclear magnetic resonance imaging (MRI) and, more particularly, to extended-linear polymeric contrast agents for magnetic resonance imaging of tumors and methods of synthesizing such agents. Linear extended polymeric paramagnetic chelates for use as MRI contrast agents are synthesized by conjugating DTPA chelator moieties to higher than 90% of the monomer residues of the polyamino acid backbone chain. The resulting polymer can be labeled with Gd, since each chelator moiety holds a Gd ion, and the resulting conformation is of an unfolded, extended linear type, capable of entering small pores and moving around obstacles in the extracellular space of tissues. The efficient production of these extended polymers is critical for the application of such contrast agents to medical imaging. One such agent is a reptating polymer containing technetium-99.