¹³C MRI of hyperpolarized pyruvate at 120 µT

Nuclear spin hyperpolarization increases the sensitivity of magnetic resonance dramatically, enabling many new applications, including real-time metabolic imaging. Parahydrogen-based signal amplification by reversible exchange (SABRE) was employed to hyperpolarize [1-¹³C]pyruvate and demonstrate ¹³C imaging in situ at 120 µT, about twice Earth's magnetic field, with two different signal amplification by reversible exchange variants: SABRE in shield enables alignment transfer to heteronuclei (SABRE-SHEATH), where hyperpolarization is transferred from parahydrogen to [1-¹³C]pyruvate at a magnetic field below 1 µT, and low-irradiation generates high tesla (LIGHT-SABRE), where hyperpolarization was prepared at 120 µT, avoiding magnetic field cycling. The 3-dimensional images of a phantom were obtained using a superconducting quantum interference device (SQUID) based magnetic field detector with submillimeter resolution. These ¹³C images demonstrate the feasibility of low-field ¹³C metabolic magnetic resonance imaging (MRI) of 50 mM [1-¹³C]pyruvate hyperpolarized by parahydrogen in reversible exchange imaged at about twice Earth's magnetic field. Using thermal ¹³C polarization available at 120 µT, the same experiment would have taken about 300 billion years.