MAGNETIC-RESONANCE SPECTROSCOPY (MRS) IN THE EVALUATION OF PEDIATRIC BRAIN-TUMORS .1. INTRODUCTION TO MRS

Magnetic resonance spectroscopy (MRS) provides a means to assess funct ional (metabolic activity) of the brain. It is now possible to perform MRS in a clinical setting with the use of an inexpensive software pac kage called Proton Brain Exam/Single Voxel (PROBE/SV) developed by Gen eral Electric Medical System for use on their 1.5-T MR scanner, We hav e used PROBE for over a year and have found it to be useful in the eva luation of brain abnormalities, Most of our experience with MRS has be en in the evaluation of children with brain tumors, In this first arti cle of a two-part series, a simplified introduction to single-voxel MR S is presented, including: 1) the differences in the normal MRS spectr a of the brains of infants, children, and adults demonstrating the var iation in peaks of the common metabolites (N-acetylasparate, creatine, and choline); 2) the two types of MRS pulse sequences, stimulated ech o acquisition mode (STEAM), a T1-weighted sequence, and point resolved spectroscopy (PRESS), a T2-weighted sequence; and 3) some of the fact ors that influence the production of diagnostic and nondiagnostic spec tra, Part Two will report findings on the efficacy of MRS in children with brain tumors. With a basic understanding of MRS, the abnormal spe ctra in the diagnosis of brain tumors can be appreciated.