Assessing the effect of anesthetic gas mixtures on hyperpolarized 13C pyruvate metabolism in the rat brain
Richard Healicon, Catriona H. E. Rooney, Vicky Ball, Ayaka Shinozaki, Jack J. Miller, Sean Smart, Daniel Radford-Smith, Daniel Anthony, Damian J. Tyler, James T. Grist
Abstract
Purpose
To determine the effect of altering anesthetic oxygen protocols on measurements of cerebral perfusion and metabolism in the rodent brain.
Methods
Seven rats were anesthetized and underwent serial MRI scans with hyperpolarized [1–13C]pyruvate and perfusion weighted imaging. The anesthetic carrier gas protocol used varied from 100:0% to 90:10% to 60:40% O2:N2O. Spectra were quantified with AMARES and perfusion imaging was processed using model-free deconvolution. A 1-way ANOVA was used to compare results across groups, with pairwise t tests performed with correction for multiple comparisons. Spearman’s correlation analysis was performed between O2% and MR measurements.
Results
There was a significant increase in bicarbonate:total 13C carbon and bicarbonate:13C pyruvate when moving between 100:0 to 90:10 and 100:0 to 60:40 O2:N2O % (0.02 ± 0.01 vs. 0.019 ± 0.005 and 0.02 ± 0.01 vs. 0.05 ± 0.02, respectively) and (0.04 ± 0.01 vs. 0.03 ± 0.01 and 0.04 ± 0.01 vs. 0.08 ± 0.02, respectively). There was a significant difference in 13C pyruvate time to peak when moving between 100:0 to 90:10 and 100:0 to 60:40 O2:N2O % (13 ± 2 vs. 10 ± 1 and 13 ± 2 vs. 7.5 ± 0.5 s, respectively) as well as significant differences in cerebral blood flow (CBF) between gas protocols. Significant correlations between bicarbonate:13C pyruvate and gas protocol (ρ = −0.47), mean transit time and gas protocol (ρ = 0.41) and 13C pyruvate time-to-peak and cerebral blood flow (ρ = −0.54) were also observed.
Conclusions
These results demonstrate that the detection and quantification of cerebral metabolism and perfusion is dependent on the oxygen protocol used in the anesthetized rodent brain.