Correlative Study on Abnormal Tumor Vascularity and Metabolism

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Recent progress of the imaging diagnosis has already established to detect the existence of tumor and its degree of extension. However, in order to select and evaluate the adequate therapeutic regimen, further specified information characterized by physiological state of the tumor such as perfusion and metabolic state should be known. On this line, to understand physiological environment of the tumor as a mass of tumor cells, correlative studies on abnormal vascurality and high enagy metabolism were perfomed at present. A series bf tumor bearing nude mice were subjected to examine using MR contrast enhancement study as well as hydrogen clearance method to evaluate perfusion status, and ^<31>P or ^<>H MR spectroscopy (MRS) to evaluate energetic metabolism. These physiological parameters of the tumor insitu were observed during tumor growth and after therapeutic intervention such as radiation and hyperthermia. During tumor growth, tumor perfusion became insufficient and resulted in anerobic metabolic state oh the whole, and these were improved by irradiation as has been hypothesized by rexygenation process. However, after application of hyperthermia, complete ischemia consequent with metabolic decline were induced. Combined application of these two intervention with opposite effect on the tumor, namely, metabolic activation or decline, revealed additive effect without cancellation, each other. Thus, present result indicated that a growing tumor became heterogenous composing of different perfusion state with different metabolic state, and, therefore, different therapeutic intervention was necessary to induce additive effect on the whole. Futher investigation concerning tumor heterogeneity on the ground of macropathology should be necessary to establish adequate selection of therapeutic intervention. On this line, noninvasive imaging of metabolites such as chemical shift imaging (CSI) using clinical MRI should be completed as a next step.