Magnetic resonance spectroscopy.

Magnetic resonance spectroscopy (MRS) complements magnetic resonance imaging (MRI) as a non-invasive means for the characterization of tissue. While MRI uses the signal from hydrogen protons to form anatomic images, proton MRS uses this information to determine the concentration of brain metabolites such as N-acetyl aspartate (NAA), choline (Cho), creatine (Cr) and lactate in the tissue examined. The most widely used clinical application of MRS has been in the evaluation of central nervous system disorders.MRS has its limitations and is not always specific but, with good technique and in combination with clinical information and conventional MRI, can be very helpful in diagnosing certain entities. For example, a specific pattern of metabolites can be seen in disorders such as Canavan's disease, creatine deficiency, and untreated bacterial brain abscess. MRS may also be helpful in the differentiation of high grade from low grade brain tumors, and perhaps in separating recurrent brain neoplasm from radiation injury.