Abstract
The shift reagents thulium(III) 1,4,7,10βtetraazacyclododecane N, Nβ², Nβ³, Nβ΄ tetramethylenephosphonate (TmDOTPS^5β^), and dysprosium(III) triethylenetetraminehexaacetate (DyTTHA^3β^) are compared in this work for their uses in sodium chemical shift imaging (NaCSI). In a series of experiments using phantoms we evaluated the relative contributions of bulk magnetic susceptibility (BMS) effects and hyperfine shifts to the induced ^23^Na chemical shift for these two shift reagents. The ratios of BMS effects to hyperfine shifts suggest that TmDOTP^5β^ should be a more effective shift reagent than DyTTHA^3β^ for ^23^Na NMR spectroscopy as well as NaCSI. The dependence on pH and free Ca^2+^ concentration of the ^23^Na NMR frequency shift induced by TmDOTP^5β^ was evaluated. It was found that TmDOTP^5β^ produces good spectral resolution under physiologic conditions. Examples presented from in vivo NaCSI experiments using TmDOTP^5β^ to study diffusion in the posterior chamber of the rabbit eye and to monitor the rate of clearance of aqueous fluid from the anterior chamber demonstrate the effectiveness of this new shift reagent and of the NaCSI technique for in vivo studies. Β© 1992 Academic Press, Inc.