| Research Abstract |
Radiation energy directly reaches tissue cells within irradiated area, while drug delivery depends on blood circulation.
Even the same dose is absorbed, however, the response of the tissues depends on their intrinsic radiosensitivity and physiological factors such as oxygen tension. Oxygen tension, in turn, depends on the oxygen supply through blood flow and the oxygen consumption reflecting the metabolic activity of the tissue.
In radiation therapy of tumors what is essential is to kill tumor cells effectively without severe damage on normal tissues involved. The differential outcome of irradiation could be attained by fractionated irradiation utilizing biological/physiological difference between tumor tissues and normal ones.
The aim of the present project has been 1) to analyze oxygen tension, energy level, and blood flow in normal and tumor tissues, 2) to clarify the differential changes in these parameters between the two kinds of tissues after irradiation, and, through the results obtained above, 3) to establish a predictive assay system which would be applicable to human subjects.
The materials in the project were mouse fibrosarcoma NFSA2ALM1 and squamous cell carcinoma NRS1 transplanted in the legs of C3H/He mice.
Oxygen tension, energy level (revealed by ^<31>P-MRS), blood flow in normal and tumor tissues, and growth of tumors have been analyzed and basic data were collected. Furthermore, some information on changes in oxygen tension and energy level after irradiation was also obtained. The analysis of the process of "reoxygenation" after irradiation and the comparison of the results to the previous information based on clonogenic assay has been initiated. Further investigation should, however, be needed to obtain a final conclusion.
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