腔道肿瘤微波热疗中有效治疗体积与冷却水温关系研究

Study on the relationship of effective therapeutic volume and water cooling temperature for intracavitory microwave hyperthermic oncology

肿瘤热疗可用活组织中的有效治疗深度ＥＴＤ（如： 定义为温度在４１～４５℃范围的距离）和有效治疗体积ＥＴＶ（定义为相应于有效治疗温度范围的体积）来衡量一次加热治疗的优劣及满意程度，但在实测时常难以实现。本文根据腔内水冷式微波偶极子辐射器近场辐射模型，求解生物介质热传导方程，运用数值计算方法得到水冷式腔道辐射器在等效组织模型中的稳态温度分布； 并对腔道肿瘤微波热疗时有效治疗体积与冷却水温关系进行仿真计算研究。结果表明：水冷可改善热区温度分布，使径向最高温度点由无水冷时贴近辐射器壁向组织深部迁移（本文示例当冷却水温Ｔｃ＝ １６℃时可达６ ｍ ｍ 以远）；径向治疗深度比无水冷时向组织内部扩展（上述冷却水温下可达３～４ ｍ ｍ 左右）； 相应的有效治疗体积则比无水冷时增加（上述条件下约为３９％ ）； 降低冷却水温（本文示例从１６℃降至１０℃）， 则相应的有效治疗深度又可向组织内部扩展； 有效治疗体积还可增加（约再增３３％ ）。由此引伸出在一次加热治疗时，若采取两步加热法， 即先用低功率、无水冷加热，后用高功率有循环水冷的加热程序，则总有效治疗体积可比完全无水冷时扩大１．２４ 倍（约增加４．３ ｃｍ ３）。

The concepts of effective therapeutic depth (defined as the distance in which, the temperature is in 41℃～45℃) and the effective therapeutic volume ( defined as the volume in which, the temperature is in 41℃～45℃) are offen used to test the heating properties in the clinics of hyperthermic oncology. In the present paper, an insulated, water cooled dipole radiating in a biological tissue, is analyzed with a theoretical electro magnetic model. The temperature distribution is calculated taking into account the effect of the water flowing inside the applicator, and compared with the temperature distribution of no water cooled radiating dipole and with different water cooling temperature. It has been shown that, the temperature distribution will be improved on the extension of the effective therapy depth due to the effect of water cooled. The water cooling effect mainly makes the highest temperature point move from the nearest place of the applicator′s wall when there is no water cooled into the deeper region (for the example illustrated in this paper, the increased distance was more than 6 mm),and the therapy depth extend to the inner tissues (about 3～4 mm),thus the coresponding therapeutic volume be in creased than that of no water cooled (about 39%).If the water cooling temperature is lower (for example, from 16℃ lower to 10℃),then the therapy depth would be extended (about 2 mm),the coresponding therapeutic volume be increased (about 33%).If the heating program is applied according to following schedule: firstly heat with small power and no water cooling, then heat with larger power and water cooling, the total effective therapy volume will be increased by 1.24 times than that no water cooled (about increased by 4.3 cm 3 ). The numerical calculated results are comformed with the equivalent muscle phantom experiment and clinical practices.