Applications of MRS in the evaluation of focal malignant brain lesions

Magnetic resonance spectroscopy (MRS) has clinically been most extensively used for assessing brain disorders, particularly tumors. With 1-H spectroscopy at intermediate echo times, resonances from choline, creatine, N-acetyl-aspartate (NAA), lactate, and free fatty acids can be resolved well enough to assist in diagnosis under routine conditions. Generally, an increased concentration of choline is found in all primary and secondary brain tumors, and the degree of increase correlates with the degree of anaplasia. Further indicators of anaplasia are the presence of lactate, indicating hypoxia, and of fatty acids, indicating necrosis. According to literature, the sensitivity of a combination of proton spectroscopy with contrast-enhanced dynamic susceptibility-weighted imaging for high-grade components in gliomas is better than conventional contrast-enhanced imaging alone. Today, proton spectroscopy is clearly indicated for differentiating radiation-induced damage from recurrences of irradiated brain tumors.