Soft-tissue sarcomas: detection of metabolic heterogeneity with P-31 MR spectroscopy

Regional variations in metabolic parameters derived with multivoxel, localized phosphorus-31 magnetic resonance (MR) spectroscopy in spontaneous human-soft-tissue sarcomas were compared with variations in the same parameters in normal human legs. In addition, multivoxel P-31 MR spectroscopy of transplanted rodent sarcomas and microelectrode measurement of pH and PO2 in several locations within them were performed, and, when appropriate, results were compared with the clinical data. Striking voxel-voxel variability in parameters derived with P-31 spectroscopy was found in tumors, with less marked variability seen in normal legs. In the rodent tumors, spatial variations also were found in pH and PO2 measured by means of microelectrodes. These data are consistent with the results of regional measurements in tumors by means of other methods and suggest that clinical MR spectroscopic studies of tumors may need to consider the variability within malignant lesions.