PDP1 and neoplasm: Lactate labelling from hyperpolarized [1‐13C] pyruvate in tumour models has previously been shown to be dependent on the level and activity of the lactate dehydrogenase enzyme, total lactate pool size and cofactor (NADH) levels.34, 35 Similarly, levels of active PDH enzyme have been shown to correlate with PDH flux measurements using hyperpolarized [1‐13C]pyruvate,16, 36 demonstrating the validity of such imaging to determine enzyme flux in vivo.