Study on Cooling Effect of Intratumoral Blood Flow During Hyperthermia

(1)采用背部移植瘤的DONRYU大鼠（8周龄）。植入测温传感器和血流传感器，用2450MHz微波加热至43ºC。同时用股动脉导管监测血压。当肿瘤内温度达到平衡时，血管紧张素ii的使用使血压升高。结果肿瘤内血流量增加，但瘤内温度几乎不变。(2)加热肿瘤可显著提高大鼠体温。所以流入肿瘤的血液温度应该很高。因此，我们无法验证关于肿瘤内血流冷却机制的假设。(3)在实验开始时，我们认为血流与肿瘤组织之间的热传导是解释尽管血压高但肿瘤内温度不下降的重要原因。但我们意识到，如果肿瘤血管的直径随着肿瘤内温度的变化而变化，则可以解释这些病例。高血压使肿瘤内血流量增加，使肿瘤血管冷却。如果降温使血管收缩，肿瘤血流量减少。简而言之，高血压不会增加肿瘤的血流量，因此肿瘤内温度不会下降。(4)为了验证以上任何一种假设，血液必须在血液进入肿瘤之前立即冷却到37^ C。但是控制大鼠血流温度的装置并不容易制造，所以我们无法在本实验中制备。

(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.