The Spin-Lattice Relaxation of Hyperpolarized $^{89}$Y Complexes

Y suitable for fast CSI techniques using flyback gradients. The development of new 89 Y complexes with even longer T1 values is desirable. The design of such complexes relies upon understanding the mechanism(s) responsible for longitudinal relaxation. However, measuring such long relaxation times with thermally polarized 89 Y requires days or weeks, rendering such an approach inefficient. We have observed that the accuracy of T1 measurements in hyperpolarized 89 Y solutions strongly depends upon appropriate choice of experimental parameters. Here we report an approach to T1 measurements. This method enabled an analysis of relaxation mechanisms by selective deuteration of the ligand backbone, the solvent or both. Initial results are reported for both open chain and macrocyclic Y(III) complexes that can be used for in vivo applications. The ligands examined are DTPA, EDTA, uniformly deuterated EDTA, and DOTA (Figure 1). METHODS T1 measurements of hyperpolarized 89 Y samples were conducted at room temperature in a 9.4T field using a Varian VNMRS console and 10mm probe tuned to 89