The development and characterization of a macrocyclic polyaminocarboxylic acid and its metal complexes as potential nuclear magnetic resonance imaging agents

Diethylenetriaminepentaacetatogadolinium(III) [Gd(III)DTPA] is currently undergoing clinical trials as a magnetic resonance imaging (MRI) agent due to its remarkably high stability in-vitro and because of its high relaxivity (R₁) value. The goal of this research was to synthesize and characterize a new macrocyclic polyaminocarboxylic acid whose Fe(III), Gd(III), and Mn(II) complexes would exhibit comparable stabilities in-vitro as well as comparable R₁ values to the diethylenetriamine pentaacetic acid (DTPA) analogues. By obtaining and comparing the R₁ values of metal complexes of 1,4,7,10,13,16-hexaazacyclooctadecane- N,N',N'' ,N'' ', N'''' ,N'"" - hexaacetic acid(OHA)w ith those of the DTPA analogues, this research qualifies the excellent potential of metal OHA complexes to be effective clinically as MRI agents.