Proton MR Spectroscopy

Nuclear magnetic resonance spectroscopy (MRS) has been in use in biochemistry labs for more than 50 yr. In its earlier years, it was used primarily for in vitro chemical analysis of small samples. Magnetic resonance imaging (MRI) is a powerful imaging technique that combines exquisite sensitivity to soft tissue contrast with the ability to demonstrate anatomy in many different planes and projections. MRS as a technique for in vivo sampling of biological tissue provides another piece of information, revealing the biochemical changes occurring in the pathological region. The advantages of MRS in comparison with other techniques that provide metabolic information (such as positron emission tomography [PET] or single-photon emission computed tomography [SPECT]) lies in the fact that MRS can be obtained during the same session as MRI. With newer MRS techniques it is possible to sample the entire lesion and its surroundings and cross-reference them to MR images; this enables us to obtain spectra belonging to many small region of the lesion (generally about 1 cm3). The spectra obtained with this whole brain technique can be compared with spectra obtained from the same exact location after therapeutic intervention, thus allowing us to see the effect of certain therapeutic interventions. MRS can be used in differentiation of similar-appearing pathology (infarct from tumor, tumor from abscess). In certain pathological conditions the MR spectrum is virtually diagnostic. Moller-Hartmann et al. (1) report that added information provided by spectroscopy led to approx 15% more correct diagnoses and 6% fewer incorrect diagnoses. In our current discussion, we consider only proton MRS. Sodium, carbon, and phosphorus MRS have yet to find wide clinical application.