Mitochondrial function in the brain can be measured with magnetisation transfer 31P-MRS. The conventional approach to magnetisation transfer incurs lengthy acquisition times, limiting the available spatial information. An accelerated approach, based on kinetic modelling, allows the technique to be extended to a multi-voxel implementation. Both approaches were applied in a group of healthy subjects to measure the rate of the creatine kinase reaction. There was good agreement between the reaction rates measured with the two methods in equivalently positioned voxels, validating the use of the accelerated approach to provide greater spatial resolution in future patient studies.