Reports on gadolinium deposits in the body and brains of adults and children who underwent contrast-enhanced MRI examinations warrant development of new, metal free, contrast agents for MRI. Nitrate is an abundant ion in mammalian biochemistry and sodium nitrate can be safely injected intravenously. We show that hyperpolarized [ 15 N]nitrate can potentially be used as an MR tracer. The 15 N site of hyperpolarized [ 15 N]nitrate showed a T 1 of more than 100 s in aqueous solutions, which was prolonged to more than 170 s below 20 °C. Capitalizing on this effect for polarization storage we obtained a visibility window of 9 min in blood. Conversion to [ 15 N]nitrite, the bioactive reduced form of nitrate, was not observed in human blood and human saliva in this time frame. Thus, [ 15 N]nitrate may serve as a long-lived hyperpolarized tracer for MR. Due to its ionic nature, the immediate applications appear to be perfusion and tissue retention imaging.
Bibliographical noteFunding Information:
This project has received funding from the European Research Council (ERC) under grant agreement No. 338040 to R.K-B, from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 667192 and from the Israel Science Foundation under grant agreement number 1379/18.
© 2019 Elsevier Inc.
- Dissolution-dynamic nuclear polarization
- Nitrate and nitrite ions
- T relaxation
- Tissue retention