Gray and White Matter Spectrum
Figure 1. Results of a single hydrogetn MRSI examination of a healthy subject who consumed alcohol before the study.
(A) For comparison, a typical magnetic resonance image from the hydrogen signal of water in the brain. Superimposed on this image is rectangle corresponding to the region from which data are obtained during MRSI. The spectroscopy volume is selected well inside the brain, because an alcohol signal from brain close to the skin ma be obscured by signals from scalp fat (seen around the perimeter of the image in C).
(B) The spectroscopic image obtained from the normal distribution of the hydrogen signal of the chemical compound NAA located in the brain region outlined on image A. Within the spectroscopy retangle (see color scale on right side), red indicates a high concentration of NAA; yellow and green represent successively lower concentrations. An outline of the head obtained from the image in A is superimposed in red lines to facilitate its comparison with the NAA image.
(C) Spectroscopic image obtained from the hydrogen signal of alcohol in the rectangular region. Inside this spectroscopy volume, the highest alcohol concentration (shown by red and orange colors) is found in a specific tissue (i.e., gray matter) along the midline between the two brain hemispheres, whereas lower concentrations are found in anoter type of tissue (i.e., white matter).*
(D) Two representative spectra obtained from predominatly gray and white matter at locations indicated by black squares on the manetic resonance image in A. Note the three characteristic brain resonances of hydrogen-containing compunds (labled Cho, Cr, and NAA) and the typical peak from alcohol on the spectra's right side. The stronder alcohol signal from the gray-matter spectrum, compared with that from the white-matter spectrum, suggests a higher concentration of alcohol in the gray matter.
MRSI = manetic resonance spectrocopic imaging; MRS = magnetic resonance spectroscopy; NAA = N-acetylasartate; Cho = choline-containing compounds; Cr = creatine-containing compunds.