Hyperpolarization and 1H-based detection of [15N]carnitine, a new long-lived metabolic imaging probe

¹³C hyperpolarization has opened the door for real-time MR metabolic imaging but remains limited by T₁'s of approximately one minute or less. ¹⁵N offers potentially much longer T₁'s, but suffers from poor intrinsic sensitivity and small chemical-shift separation. We have hyperpolarized L-[¹⁵N]carnitine-d₉, a novel metabolic imaging probe, and found ultra-long T₁'s of 210s (in H₂O) / 160s (in vivo). We also demonstrate successful ¹⁵N->¹H hyperpolarization transfer for enhanced sensitivity of detection as well as larger chemical-shift separation among metabolites. The long signal lifetime and excellent safety profile of [¹⁵N]carnitine suggest great potential for metabolic imaging investigations and future clinical translation.