QUANTITATIVE PROTON SPECTROSCOPY OF CANINE BRAIN - IN-VIVO AND IN-VITRO CORRELATIONS

Quantitative, single-voxel proton NMR spectroscopy of normal brain was performed in five adult beagle dogs using the cerebral water signal a s an internal intensity reference. The same brain regions were then ra pidly isolated and frozen using a pneumatic biopsy drill, perchloric a cid extracted, and analyzed by biochemical assay and high-resolution N MR spectroscopy. The concentrations of the major resonances in the in vivo and in vitro spectra were compared, and good agreement was found between the different measurements. The in vivo spectra contained thre e peaks at 3.21, 3.04, and 2.02 ppm, which are usually assigned to tri methylamines (TMA), creatines, and N-acetyl derivatives (NAc), which c orresponded to be the following metabolite concentration values: 1.7 /- 0.6, 7.7 +/- 2.1, and 10.9 +/- 2.7 mu mol/g wet weight respectively . In vitro, the following metabolite concentrations were measured: gly cerophosphocholine (GPC) 1.3 +/- 0.2, phosphocholine (PC) 0.5 +/- 0.1, phosphocreatine (PCr) 2.6 +/- 0.4, creatine (Cr) 5.9 +/- 1.4, and N-A cetyl aspartate(NAA) 8.9 +/- 1.8 mu mol/g wet weight. Therefore, the 3 .21 ppm resonance observed in the in vivo spectrum is predominantly GP C and PC in a ratio of 2.6:1, the 3.04 ppm resonance is Cr and PCr in a ratio of 2.3:1, and the 2.02 ppm resonance is predominantly (approxi mate to 80%) NAA with small contributions from N-acetylaspartylglutama te (NAAG) and glutamate. The data presented here validate the techniqu e of water referencing as a simple and convenient means of quantitatin g single-voxel in vivo proton NMR spectra of the brain.