Magnetic resonance spectroscopy (MRS) in the evaluation of pediatric brain tumors, Part I: Introduction to MRS.

Magnetic resonance spectroscopy (MRS) provides a means to assess functional (metabolic activity) of the brain. It is now possible to perform MRS in a clinical setting with the use of an inexpensive software package called Proton Brain Exam/Single Voxel (PROBE/SV) developed by General Electric Medical System for use on their 1.5-T MR scanner. We have used PROBE for over a year and have found it to be useful in the evaluation of brain abnormalities. Most of our experience with MRS has been in the evaluation of children with brain tumors. In this first article of a two-part series, a simplified introduction to single-voxel MRS is presented, including: 1) the differences in the normal MRS spectra of the brains of infants, children, and adults demonstrating the variation in peaks of the common metabolities (N-acetylasparate, creatine, and choline); 2) the two types of MRS pulse sequences, stimulated echo acquisition mode (STEAM), a T1-weighted sequence, and point resolved spectroscopy (PRESS), a T2-weighted sequence; and 3) some of the factors that influence the production of diagnostic and nondiagnostic spectra. Part Two will report findings on the efficacy of MRS in children with brain tumors. With a basic understanding of MRS, the abnormal spectra in the diagnosis of brain tumors can be appreciated.