Detection of acute kidney injury with hyperpolarized [ 13 C, 15 N]Urea and multiexponential relaxation modeling.

Purpose: To assess the utility of Laplacian fitting to describe the differences in hyperpolarized [ ¹³ C, ¹⁵ N]urea T ₂ relaxation in ischemic and healthy rodent kidneys.
Methods: Six rats with unilateral renal ischemia were investigated. [ ¹³ C, ¹⁵ N]Urea T ₂ mapping was undertaken with a radial fast spin echo method, with subsequent postprocessing performed with regularized Laplacian fitting.
Results: Simulations showed that Laplacian fitting was stable down to a signal-to-noise ratio of 20. In vivo results showed a significant increase in the mono- and decrease in biexponential pools in ischemia reperfusion injury kidneys, in comparison to healthy (14 ± 10% versus 4 ± 2%, 85 ± 10% versus 95 ± 3%; P < .05).
Conclusion: We demonstrate, for the first time, the differences in multiexponential behavior of [ ¹³ C, ¹⁵ N]urea between the healthy and ischemic rodent kidney. The distribution of relaxation pools were found to be both visually and numerically significantly different. The ability to improve the information level in hyperpolarized MR, by using the relaxation contrast mechanisms is an appealing option, that can easily be adopted in large animals and even in clinical studies in the near future.
(© 2019 International Society for Magnetic Resonance in Medicine.)