JnJ Logo JAS MR Spectroscopy Program:

Proton Magnetic Resonance Spectroscopy (MRS)

The principles of magnetic resonance were used to measure chemical structure and composition for over 30 years prior to their use in the development of MRI. With the availability of capable clinical MRI/MRS systems, and techniques to readily isolate chemical measurements to specific regions in the brain, practical in vivo measurements of tissue metabolite levels are available for the study of normal and pathological processes.

The basic capabilities of the MRI/MRS system have been augmented by a large number of acquisition sequences and procedures that allow high quality localized metabolite spectra to be obtained within the duration of a normal imaging examination. Full facilities for acquisition and processing of single-voxel (SVS) and 1D or 2D spectroscopic imaging (MRSI) data are available. The MRS techniques are used in several research programs at the Facility.

As expected, Facility work in MRS applies primarily to the brain. However, similar technology is applied to other organ systems where work correlating morphological and biochemical changes with drug treatment can be used as a model for brain tumor radiation or chemotherapy.

MRS FIG1 There are currently two main focuses for the MRS brain research at the Facility. The first is in the measurement of the biochemical characteristics of primary and metastatic brain tumors. The unique characteristics of tumor spectra have been demonstrated during the course of our participation in multicenter MRS clinical trials. (Figure 1) The extension of that work is currently towards the evaluation of MRS as an effective tool for discrimination between tumor recurrence and the effects of radiation treatment. This is often a difficult clinical decision as there may be similar MRI image appearance. The results of MRS examination of clinical patients is being correlated with those from SPECT in order to determine the effectiveness of MRS as a routine clinical tool in these cases.

Additional work is underway applying these techniques to study stroke, white-matter diseases, and traumatic brain injury.

MRS FIG2 The second MRS focus employs functional localization, typically by MEG, to identify regions of interest for further biochemical interrogation by MRS. With current procedures, MRS or MRSI metabolite information cannot practically be obtained throughout the head at the same resolution as MRI image information. The functional localization is used to identify a smaller region of interest where MRS measurements can be made more efficiently. The information obtained provides insight into the biochemical processes accompanying neural activation of normal and abnormal brain regions. (Figure 2)

Current research at the Facility is investigating the biochemical processes in the tissue at the epileptic seizure focus identified by MEG. The results of this study will help validate MEG localization in these cases, correlate metabolite levels with electrophysiological changes, and give insight into the effectiveness of MRS as a focus localization modality with and without MEG guidance.

Technical development and experimental research is ongoing to improve MRS spatial resolution (eg combined SVS and MRSI acquisitions), quality (e.g., rf pulse design and water suppression methods), analysis (e.g., signal processing procedures), and clinical application (e.g., automated examination procedures).

Last Modified: July 14, 1999 Copyright 1999 John A Sanders, VAMC