The combination of magnetic resonance spectroscopy (MRS) and imaging (MRI) has led to mapping metabolites from normal and neoplastic tissue within the time limits of a routine study. MRSI (magnetic resonance spectroscopy imaging) detects metabolites that contain
protons,
phosphorus,
fluorine, or other nuclei. The uniqueness of the information available in vivo and in a non-invasive manner encouraged radiologists and oncologists to apply MRSI in research and clinical practice. Both (1)H- and (31)P-MRS have revealed significant disturbances in
amino acids,
lipids, and
phosphorus-containing metabolites within
tumors.
Phosphocreatine is often diminished in
neoplasms compared to their primary host or surrounding tissues. However, the reduction of the compound does not appear to be closely correlated to the degree of
malignancy. Moreover, abnormalities in (31)P spectra from
neoplasms are shared by other disorders. Changes in high-energy
phosphate levels almost invariably occur with radio- and
chemotherapy of
tumors. The spectroscopic alterations are often seen before any variations in
tumor size and shape can be detected. However, opposite responses can be associated with the same clinical outcome. (1)H-MRS has been successfully used to quantify the extent of neuronal cell loss imposed on the brain during
radiotherapy. Recently, MRSI was successfully integrated into
radiotherapy planning in
prostate cancer patients. (19)F-MRS opens access to artificially induced fluorocompounds such as
5-fluorouracil and its metabolites.