Proton Magnetic Resonance Spectroscopy in Intracranial Gliomas

Abstract

Recent MRI advances have focused on the development and application of molecular and physiological imaging capabilities. One of these relatively new MRI methods, Magnetic Resonance Spectroscopy (MRS) reflects the continuing evolution from purely anatomic to physiological and molecular imaging of the brain. Magnetic Resonance Spectroscopy yields images of the distribution and concentration of naturally occurring molecules such as N-acetyl aspartate (NAA) (one of the most abundant amino acids in the brain), choline (Cho) (a key constituent of cell membranes), lactate (Lac) (a reflection of anaerobic metabolism) and Creatines (Cr). It has been suggested that the sum of Cr and Phosphocreatine is relatively constant in the human brain, and for this reason Cr is often used as a reference signal, and it is a common practice for metabolite ratios to be expressed as a ratio relative to Cr. However, with the development of quantitative analysis techniques, it is clear that total Cr is not constant, both in different brain regions and in pathological processes, so the assumption of Cr as a reference signal should be used with caution. It is well known that gliomas represent the most common type of primary intracranial tumors. The establishment of an accurate diagnosis, the preoperative evaluation of tumor metabolism and the obtaining information regarding tumor histological grade, may increase the efficacy of the currently employed treatments and eventually improve the overall clinical outcome in gliomas cases. Magnetic Resonance Spectroscopy may substantially improve the non-invasive categorization of human brain tumors, especially gliomas. The utilization of MRS (coupled to conventional MRI techniques) in the evaluation of tumors provides greater information concerning tumor activity and metabolism. In addition, it may provide valuable information regarding the tumor response to the employed treatments.