Oxygenation and metabolic status of KHT tumors as measured simultaneously by 19F magnetic resonance imaging and 31P magnetic resonance spectroscopy

To evaluate the relationship between the partial pressure of oxygen (pO2) and the energy-related phosphorous metabolites in individual KHT murine sarcomas more clearly, the spatial distributions of pO2 were obtained simultaneously with 31P magnetic resonance spectra, and repeatedly as a function of growth. The pO2 maps, derived from serial images of the spin-lattice relaxation times of sequestered perfluorocarbon emulsions, were heterogeneous spatially, which is characteristic of solid tumors. Collectively, the median pO2 of the seven KHT tumors of mass varying from 0.2 to 1.8 g decreased from 60 to 0 mmHg, but it increased in one of five tumors which were followed in the growth study. The pHMRS and the high-energy ratio of phosphocreatine + nucleoside triphosphates to total observed phosphorous (TP) dropped on average as a function of tumor growth, while the low energy ratio of Pi to TP increased. Also, for the tumors as a whole, the pH and high-energy ratio increased with increasing median pO2 while the low energy ratio decreased, but the 31P values of some tumors did not follow this general trend. These individual variations suggest the need for simultaneous and repeated measurements of phosphorous metabolites and oxygen tension for complete information regarding the tumor status in experimental studies and therapeutic procedures in humans.