Exploration of noninvasive mapping of brain pH with 31P magnetic resonance spectroscopy

Previous study of brain “potential of hydrogen” (pH) was conducted in single-voxel ³¹P magnetic resonance (MR) spectroscopy. In this study, we explored the feasibility of mapping brain pH by using multivoxel ³¹P MR spectroscopy. Firstly, phantom studies were carried out with a GE 3T MR system using 2D PRESSCSI sequence. TR was 1000 msec and TE 144 msec with 128 scan averages. Then two healthy volunteers were studied with same parameters. Data were processed offline using the SAGE/IDL program. Multivoxel spectra were analyzed and brain pH values were calculated with a standard equation. Peaks of metabolite were not homogeneous in phantom studies at this moment. There was noise for multivoxel ³¹P spectra in volunteer studies. However, phosphomonoester peak, inorganic phosphate peak, phosphodiester peak, and phosphocreatine peak can be identified. Preliminary brain pH map was generated in the volunteers. In our opinion, it is feasible to map brain pH with improved multivoxel ³¹P MR spectroscopy.