31P MRSI of the human brain: do we need 7T to detect two Pi pools, UDPG signals and determine the NAD+/NADH ratio?

All resonances in human brain ³¹P MR spectra detectable at 7T and higher can also be detected at 3T provided that ¹H decoupling, ¹H-³¹P NOE and a ³¹P receive-array are used. This includes a alkaline peak for extracellular Pi and peaks assigned to UDPG. A NAD⁺/NADH redox state similar to that reported at 7T was observed. A comparison of measured T1 values with those reported at different field strengths and NOEs measured at 3 and 7T indicates that CSA is not dominant in 31P relaxation and hence there is no sensitivity benefit from shorter T1s at higher fields.