FIG. 1.

(a) 7T MR head images showing the location of superior sagittal sinus (SSS), transverse sinus (TS), and the ³¹P saturation slabs for outer-volume-suppression (OVS). The green box in the images represents the ¹H shimming area. (b) Fully-relaxed 7T ³¹P MR spectra at long TR of 30 sec, acquired from resting human brain using a pulse-acquire sequence with (red trace) and without (blue trace) OVS saturation. Note the marked attenuation of the signals at Pi^ex and PE upon OVS saturation, while other metabolite ³¹P signals remain unchanged in reference to PCr at 0 ppm. Also note the asymmetric lineshape of the attenuated peak at PE (inset) as featured in typical membrane phospholipid signal due to chemical shift anisotropy effect. (c) The fitted ³¹P MR spectra in the chemical shift region between -4.0 and 8.0 ppm (red trace: OVS on; blue trace: OVS off). Abbreviation: PE, phosphoethenolamine; PC, phosphocholine, GPE, glycerophosphoethanolamine; GPC, glycerophosphocholine; Piⁱⁿ and Pi^ex, intra- and extracellular inorganic phosphate; PCr, phosphocreatine; ATP, adenosine triphosphate; NAD, nicotinamide adenine dinucleotide; UDPG, uridine diphosphate glucose; PME, phosphomonoester; PDE, phosphodiester; MM, macromolecules (likely from mobile membrane phospholipids).