Figure 2

Hyperpolarised [1-¹³C]pyruvate and ethyl-[1-¹³C]pyruvate imaging in rats. (A) Representative summed [1-¹³C]pyruvate and [1-¹³C]lactate volumes shown concatenated through the slice axis following [1-¹³C]pyruvate infusion. Pyruvate was seen perfusing in the approximate location of the Circle of Willis (CW) and the middle cerebral artery (MCA), along with the common carotid and the jugular vein (JV/CA). The observed lactate signal is of low SNR and approximately seen in the location of the Circle of Willis. Proton images are deliberately scaled to the same resolution as the hyperpolarized scan. (B) As above, but for a tumour-bearing animal, shown here at day 36, together with gadolinium difference image. Lactate was observed in the tumour. The colour axis is as for A Both image stacks have a reconstructed resolution of 1 × 1 × 2 mm³. The regional lac/pyr ratio was not significantly different between control and affected animals, although it significantly reduced over time (p = 0.00795 via an anova upon linear mixed effects modelling). (D,E) Example summed spectrum and peak intensity timecourses from ethyl-[1-¹³C]pyruvate infusion, after 10 Hz exponential apodization and polynomial baseline correction. Downstream metabolites are clearly visible, with the exception of bicarbonate and CO₂ which were not resolved. (F) In contrast to the predominantly vascular images of hyperpolarized [1-¹³C]pyruvate, ethyl-[1-¹³C]pyruvate freely diffuses into the brain, producing downstream pyruvate and lactate visible only in the region of disease.