A high-powered MRI is now available for clinical use - the 7tesla MRI - some are in NYC and boston, among other places. Here is a particular quote i found about the seimens 7 tesla MRI.
"With 7T MR, Gruetter and his team can evaluate a panel of 17 molecules simultaneously to provide what he calls a neuro- chemical profile, and then see how brain activation changes that profile. The pro- file includes molecules involved in energy metabolism like glucose and creatine, neurotransmitters like glutamate and gamma-aminobutyric acid (GABA), com- pounds involved in cell growth like choline or in axon growth like N-acetylaspartate, compounds involved in osmoregulation like taurine and inositol, and molecules that are antioxidants, like glutathione and vitamin C. “At 7T, we expect to be able to measure such a profile with ten Ultra-high-field Brain Imaging percent precision in a very small volume, so we might be able to measure profiles within a structure like the substantia nigra or hippocampus"
Perhaps they can also measure dopamine and or allopregnanelone, since they can measure gaba, Unless one molecule is specifically smaller then another.
More info: http://www.medical.siemens.com/webapp/w ... _10001.htm