Brice Tiret1,2, Vincent Lebon1,2, Emmanuel Brouillet1,2, and Julien Valette1,2
MRS with progressive saturation transfer was performed in the rat brain to
estimate the exchange rate between inorganic phosphate (Pi) and adenosine-tri-phosphate
(ATP). It was found that two Pi pools, tentatively intra and extracellular
pools, can be resolved at 11.7 T, and that only the intracellular Pi signal
varies with progressive saturation, while the extracellular Pi signal remains
constant. Not resolving this extracellular Pi can cause a significant bias in
the estimation of the forward constant rate of ATP synthesis.