Dynamic sodium chemical shift imaging for the study of aqueous humor flow

Ocular images were obtained using sodium chemical shift imaging (CSI) and 1,4,7,10-tetraazacyclododecane-N,N'N",N"'-tetramethylenephospho nate thulium (III) [Tm(DOTP)5-], a paramagnetic chemical shift reagent. After injecting the shift reagent into the anterior chamber of rabbits, serial imaging was done, monitoring the change in chemical shift with time. Sodium CSI produced images of the eye in three dimensions, quantitatively depicting the spatial and temporal changes in the concentration of a paramagnetic tracer substance. The Tm(DOTP)5- is eliminated from the anterior chamber by first-order kinetics with a half-life of 49 min. These data suggest that this substance is eliminated from the anterior chamber at the same rate as aqueous humor is replaced. Sodium CSI shows promise as a valuable technique for monitoring fluid dynamics in the living eye.