Study on Cooling Effect of Intratumoral Blood Flow During Hyperthermia

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(1) DONRYU rats (8 week-old) with transplanted tumor on the back were used in this experiment. The tumors were inserted with thermometry sensors and blood flow sensors and heated by 2450MHz microwave to 43^ﾟC. Blood pressure was simultaneously monitored with catheters in femoral artery. When intratumoral temperature cme to an equilibrium, blood pressure was raised by administration of AngiotensinII. Consequently blood flow in tumor was increased, but intratumoral temperature was almost unchanged.(2) By heating tumors body temperature of rats was raised remarkably. So temperature of blood flowing into tumors was supposed to be high. Therefore we could not verify a hypothesis on cooling mechnism of intratumoral blood flow.(3) At the beginning of the experiment, we thought that heat conduction between blood flow and tumor tissue was important to explain cases in which intratumoral temperature didn't fall in spite of high blood pressure. But we became aware that the cases can be explained if diameters of tumor blood vesels vary as intratumoral temperature changes. High blood pressure produces increase of blood flow in tumor, then cooling of blood vessels of the tumor. If the cooling brings the blood vessels to contraction, tumor blood flow decreases. In short, high blood pressure doesn't increase blood flo w of the tumor, therefore intratumoral temperature doesn't fall.(4) To verify either of above hypotheses, blood must be cooled to 37^ﾟC, immediately before the blood flows in tumor. But the apparatus which can control temperature of blood flow of rats are not easy to make, so we couldn't prepare it in this experiment.