Absolute quantitation of short TE brain 1H-MR spectra and spectroscopic imaging data

A method for determining the concentrations of the materials that produce the well-resolved singlet signals in short TE brain 1H MR spectroscopic examinations is presented. Concentration determination is achieved by a water-referencing procedure. The ratios of the areas of the choline, total creatine, and N-acetyl signals to that of the water signal from the same volume of interest (VOI) are determined using acquisitions with and without water suppression. The tissue concentrations of the molecules producing the three signals can then be determined if the water concentration in the VOI can be found. This is done with a density-weighted MR study. The MR study provides the ratio of the mean MR signal amplitude from the VOI to that from an external standard containing a known water concentration. The method's flexibility is illustrated by using it with two different single-volume localization schemes and spectroscopic imaging. Preliminary evaluations of accuracy and reproducibility are made in phantom, animal, and limited human studies. The method's advantages and limitations are discussed.