Magnetic resonance (MR) spectroscopy
Magnetic Resonance (MR) spectroscopy is a noninvasive diagnostic test for measuring biochemical changes in the brain, especially the presence of tumors. While magnetic resonance imaging (MRI) identifies the anatomical location of a tumor, MR spectroscopy compares the chemical composition of normal brain tissue with abnormal tumor tissue. This test can also be used to detect tissue changes in stroke and epilepsy.
How does MR spectroscopy work?
MR spectroscopy is conducted on the same machine as conventional MRI (see Magnetic Resonance Imaging). The MRI scan uses a powerful magnet, radio waves, and a computer to create detailed images. Spectroscopy is a series of tests that are added to the MRI scan of your brain or spine to measure the chemical metabolism of a suspected tumor.
MR spectroscopy analyzes molecules such as hydrogen ions or protons. Proton spectroscopy is more commonly used [1, 2]. There are several different metabolites, or products of metabolism, that can be measured to
differentiate between tumor types:
- Amino acids
- N-acetyl aspartate
The frequency of these metabolites is measured in units called parts per million (ppm) and plotted on a graph as peaks of varying height (Fig. 1). By measuring each metabolite’s ppm and comparing it to normal brain tissue, the neuroradiologist can determine the type of tissue present.