Several yttrium polyamino polycarboxylate complexes have successfully been hyperpolarized using fast dissolution dynamic nuclear polarization (DNP) NMR technique. Up to 65,000 fold 89Y NMR signal enhancement of YDOTA (DOTA = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) was achieved by establishing the optimal microwave irradiation frequency, optimizing the glassing matrix (glycerol-water), choosing a free radical polarizing agent with negligible inhomogeneous line broadening contribution to the ESR linewidth (trityl OX063), and addition of an electron T1 relaxation agent (ProHance).  Most yttrium complexes were found to have extremely long 89Y spin lattice (T1) relaxation times (around 400-500 s). The chemical shift of the Y(III)-ion appears to be very sensitive to its coordination environment as demonstrated by the wide range of 89Y chemical shifts (about 100 ppm) in structurally similar complexes. The 89Y chemical shift of YDOTP (DOTP = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetramethylenephosphonic acid) is pH dependent and shows a pH dispersion of 0.29 pH unit / ppm in the physiologically relevant pH range. MR imaging of phantoms containing hyperpolarized YDOTA was demonstrated at a concentration of 1 mM using a chemical shift imaging (CSI) sequence.

Hyperpolarized yttrium-89 complexes as potential magnetic resonance probes

247th National Meeting (2014)

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