Figure 1. Hyperpolarization and acquisition.

The [1-¹³C] pyruvate is polarized using dissolution dynamic nuclear polarization: microwave irradiation is used to transfer the high polarization of the radical achieved at high magnetic field and low temperature to the ¹³C nuclei (red circles). Following dissolution, the sample must pass a Quality Control check before injection, which measures pyruvate and residual radical concentrations, temperature, pH, and polarization. A power injector is used to deliver a bolus of pyruvate with a saline flush. An EPSI sequence is repeated to acquire 2D dynamic spectra with 1.5 cm³ nominal spatial resolution and 4.9 s temporal resolution.