1H spin-lattice relaxation in water solution of 209Bi counterparts of Gd3+contrast agents

¹H spin-lattice relaxation studies of water solutions of Bismuth-ethylenediamine-tetraacetic acid (Bi-EDTA), Bismuth-ethylenediamine-tetrakis(methylenephosphonic) acid (Bi-EDTP), Bismuth-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (Bi-DOTA), Bismuth-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrakis(methylenephosphonic acid) (Bi-DOTP) and Bismuth-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (Bi-DO3A) have been performed in order to compare Quadrupole Relaxation Enhancement (QRE) effects with Paramagnetic Relaxation Enhancement (PRE) from the perspective of exploiting the first one as a novel contrast  mechanism for Magnetic Resonance Imaging (MRI). The selected compounds can be considered as ²⁰⁹Bi counterparts of Gd³⁺ complexes. The relaxation experiments have been performed in a broad frequency range of 5kHz-30MHz. The relaxation contribution associated with QRE has been extracted from the data and compared with PRE. Similarities and differences between the two effects have been discussed.