α‐trideuteromethyl[15N]glutamine: A long‐lived hyperpolarized perfusion marker

Purpose We characterized the performance of a novel hyperpolarized perfusion marker, α‐trideuteromethyl[15N]glutamine, for direct comparison with a 13C‐based hyperpolarized perfusion marker, [13C, 15N2]urea. Methods A hardware platform and pulse sequence for in vivo 15N experiments were established. Hyperpolarized solutions of α‐trideuteromethyl[15N]glutamine and [13C, 15N2]urea were injected into healthy male Lewis rats. Kidney slice images were acquired using a single‐shot spiral readout. Both compounds were compared to determine in vivo signal lifetime and tracer distribution. Mass spectrometry was performed to evaluate excretion of the compound. Results Compared with 13C‐labeled urea, a significantly increased signal lifetime was observed. While the urea signal was gone after 90 s, decay of the glutamine compound was sufficiently slow to obtain a quantifiable signal, even after 5 min. The glutamine derivative showed strong localization in the kidneys with little background signal. Effective T1 of α‐trideuteromethyl[15N]glutamine was approximately eight‐fold higher than that of urea. Mass spectrometry results confirmed rapid excretion within the time scale of the measurement. Conclusion Hyperpolarized α‐trideuteromethyl[15N]glutamine is a highly promising candidate for renal studies because of its long signal lifetime, strong localization and rapid excretion. Magn Reson Med 76:1900–1904, 2016. © 2016 International Society for Magnetic Resonance in Medicine