Evidence of 13 C‐lactate oxidation in the human brain from hyperpolarized 13 C‐MRI

Purpose To test the hypothesis that lactate oxidation contributes to the C‐bicarbonate signal observed in the awake human brain using hyperpolarized C MRI. Methods Healthy human volunteers ( N = 6) were scanned twice using hyperpolarized C‐MRI, with increased radiofrequency saturation of C‐lactate on one set of scans. C‐lactate, C‐bicarbonate, and C‐pyruvate signals for 132 brain regions across each set of scans were compared using a clustered Wilcoxon signed‐rank test. Results Increased C‐lactate radiofrequency saturation resulted in a significantly lower C‐bicarbonate signal ( p = 0.04). These changes were observed across the majority of brain regions. Conclusion Radiofrequency saturation of C‐lactate leads to a decrease in C‐bicarbonate signal, demonstrating that the C‐lactate generated from the injected C‐pyruvate is being converted back to C‐pyruvate and oxidized throughout the human brain.