Metabolic heterogeneity in RIF‐1 tumours detected in vivo by ³¹P NMR spectroscopy

The spatial distribution of phosphate metabolites and pH within subcutaneously implanted RIF‐1 tumours was determined by 1‐dimensional phosphorus chemical shift imaging. ³¹P spectra from two to three 4 mm thick cross‐sectional slices were obtained for each tumour. Quantitative morphometry was used to estimate the amount of necrosis within those slices. A spatially heterogeneous distribution of phosphate metabolites and pH was detected in most of the tumours. Levels of necrosis ranged from 0–24% for the tumours in this study. There was no significant correlation between the extent of necrosis over this range and levels of metabolites or pH, suggesting that factors besides necrosis can contribute to spectral heterogeneity.