Measurement of unidirectional P_i to ATP flux in human visual cortex at 7 T by using in vivo ³¹P magnetic resonance spectroscopy

Taking advantage of the high NMR detection sensitivity and the large chemical shift dispersion offered by ultra-high field strength of 7 T, the effect of magnetization transfer on inorganic phosphate (P_i) resonance during saturation of γ-ATP resonance, mediated by the ATP synthesis reaction, was observed noninvasively in the human primary visual cortex by using in vivo ³¹P magnetic resonance spectroscopy. The unidirectional flux from P_i to ATP was measured by using progressive saturation transfer experiments. The cerebral ATP synthesis rate in the human primary visual cortex measured by ³¹P magnetic resonance spectroscopy in this study was 12.1 ± 2.8 μmol ATP/g per min, which agreed well with the value that was calculated indirectly from the cerebral metabolic rate of glucose consumption reported previously.