Of the 12,000 new patients diagnosed each year with a high-grade glioma, virtually all will receive some form of radiation therapy. Of these, 20 percent will develop side-effects related to the treatment that mimic tumor recurrence. As the use of new methods of radiation delivery becomes more common this percentage will increase. Thus, the development of a non-invasive technique to differentiate radiation injury from tumor recurrence is an important clinical goal. Anatomic CT and MR images are insufficient to discriminate radiation changes from recurrence. Alternative imaging modalities such as FDG PET, SPECT and MR perfusion, while sensitive, lack the specificity to make this determination. In principle, MR spectroscopy (MRS) can unambiguously identify all tissue types. However, at the conventional field strength of 1.5 Tesla, low spatial resolution and limited specificity hinder the clinical utility of MRS. They applicants hypothesize, that at a field strength of 3 Tesla, spectral dispersion and spatial resolution will be sufficient to make MRS clinically relevant for the identification of recurrent tumor and radiation change. They further hypothesize that the improved spectral resolution and sensitivity will allow them to implement EPI-based imaging methods to generate metabolite maps. Their preliminary data suggest that in vivo MRS spectral patterns at 3T reliably differentiate between tumor, radiation change and healthy tissue. Thirteen of 14 biopsy sites could be correlated with the histopathological diagnosis of presence of absence of recurrent tumor based on the ratio of the metabolites choline and creatine. To validate and expand these promising results, they will undertake the following specific aims: 1) to further characterize, non-invasively, the spectral patterns associated with normal tissue, tumor and radiation changes using in vivo proton MRS at 3T to examine patients who have been diagnosed with a glioma; 2) to develop and employ an echo-planar based spectroscopic-imaging (MRSI) protocol using oscillating gradients at 3T that will allow mapping of these spectral patterns within a clinically feasible time-frame; 3) to validate MRSI as a diagnostic method by correlating the in vivo measurements with findings from histopathology using the newly developed ex vivo MRS method of High-Resolution MAS (HRMAS) on whole-tissue biopsy samples from patients who have undergone the MRSI exam. The successful completion of this study will allow the assessment of MRSI as a diagnostic tool for distinguishing tumor recurrence from radiation change.
| Rabinov, James D; Lee, Patricia Lani; Barker, Frederick G et al. (2002) In vivo 3-T MR spectroscopy in the distinction of recurrent glioma versus radiation effects: initial experience. Radiology 225:871-9 |
| Lee, P L; Gonzalez, R G (2000) Magnetic resonance spectroscopy of brain tumors. Curr Opin Oncol 12:199-204 |
