Molecular imaging with endogenous substances

TLDR

Dynamic nuclear polarization has enabled hyperpolarization of nuclei such as 13C and 15N in endogenous substances, allowing subsecond 13C MRI. High‑resolution (~1‑mm) MRI images were acquired every 240 ms from 0–5 s after intravenous injection of hyperpolarized aqueous [13C]urea. Hyperpolarized [13C]urea achieved 10 % polarization, had a 20 s T1, and enabled 13C angiography with SNR ≈ 275 in 0.25 s, suggesting that endogenous perfusion imaging can surpass current proton techniques.

Abstract

Dynamic nuclear polarization has enabled hyperpolarization of nuclei such as 13C and 15N in endogenous substances. The resulting high nuclear polarization makes it possible to perform subsecond 13C MRI. By using the dynamic nuclear polarization hyperpolarization technique, 10% polarization was obtained in an aqueous solution of 100 mM 13C-labeled urea, ready for injection. The in vivo T1 relaxation time of 13C in the urea solution was determined to 20 +/- 2 s. Due to the long relaxation time, it is possible to use the hyperpolarized substance for medical imaging. A series of high-resolution ( approximately 1-mm) magnetic resonance images were acquired, each with a scan time of 240 ms, 0-5 s after an i.v. injection of the hyperpolarized aqueous [13C]urea solution in a rat. The results show that it is possible to perform 13C angiography with a signal-to-noise ratio of approximately 275 in approximately 0.25 s. Perfusion studies with endogenous substances may allow higher spatial and/or temporal resolution than is possible with current proton imaging techniques.