无创和微创热疗过程中的热场分布研究

发布时间：2018-06-09 12:47

  本文选题：热疗 + 有限元　； 参考：《上海交通大学》2008年硕士论文

【摘要】： 肿瘤热疗是目前肿瘤治疗的研究重点,已成为继手术、放疗、化疗之后又一重要的治癌手段。在热疗临床应用中,影响疗效的因素很多,如系统的功率、加热时间、作用方式以及组织的物性参数等,在制定治疗计划时需综合考虑这些因素。热疗分为无创和微创两种。前者以高强度聚焦超声技术为代表,后者以射频消融系统为代表。文中分别对这两个典型的热疗系统围绕上述因素展开了分析。 针对无创热疗——高强度聚焦超声技术,主要关注系统参数(主要指聚焦超声能量)对加热效果的影响,研究了聚焦超声剂量与损伤区域的关系。结果表明:为得到大小和形状相似的热损伤焦域,聚焦超声的声场强度和加热时间近似满足关系:It0.8=常数。利用公式可以进行不同声强、时间治疗方案之间的切换。另外,针对单焦点扫描情况,探讨了扫描间距对温度场分布的影响:当焦点间距为一倍的焦斑直径时,焦点处最高温度的增长率都在7%以上;随着扫描间距的增大,前面焦点的热场对后续焦点的影响变弱。因此在扫描过程中,要衡量选择合适的扫描间距,并及时调整治疗参数,避免出现过高温度。 针对微创热疗——射频消融系统,建立电热耦合有限元模型,侧重讨论了整个加热过程中,血液灌流、水冷温度等参数对热损伤的影响。得出:在水冷作用下,组织的最高温度区位于电极表面2-3mm的地方;水冷温度越低,得到的消融范围越大。当组织的血液灌流率从0变化到3.0e-3(1/s),热损伤直径缩小了33.8%,数据表明血液灌流率对于温度和热损伤体积的影响很大。文中还对两种确定热损伤边界(50℃和EM43)的方法进行了比较,探讨了它们之间的区别。 通过对这两种热疗系统的分析,建立了一套适用于两种热疗方式热场分布研究的方法,从不同角度分析了各参数对热疗的影响,期望能推动和推广热疗技术的应用。
[Abstract]:Tumor hyperthermia is the focus of cancer treatment, and has become an important means of cancer treatment after surgery, radiotherapy and chemotherapy. In the clinical application of hyperthermia, there are many factors that affect the curative effect, such as the power of the system, heating time, the mode of action and the physical parameters of the tissue. These factors should be taken into account when making the treatment plan. Hyperthermia is divided into two types: non-invasive and minimally invasive. The former is represented by high intensity focused ultrasound and the latter by radiofrequency ablation system. In this paper, the two typical hyperthermia systems are analyzed around the above factors. For the non-invasive hyperthermal-high intensity focused ultrasound (HIFU) technology, the influence of system parameters (mainly focused ultrasound energy) on the heating effect is mainly concerned. The relationship between the dose of focused ultrasound and the damage area was studied. The results show that in order to obtain the thermal damage focal region of similar size and shape, the sound field intensity and heating time of focused ultrasound approximately satisfy the relation of: I t 0.8 = constant. The formula can be used to switch between different sound intensity and time therapy. In addition, the effect of scanning spacing on the temperature field distribution is discussed. When the focal spot diameter is double, the growth rate of the highest temperature at the focal point is above 7%, and with the increase of the scanning distance, The effect of the thermal field of the front focus on the subsequent focus becomes weaker. Therefore, in the process of scanning, we should measure the appropriate scanning distance and adjust the treatment parameters in time to avoid excessive temperature. For the minimally invasive hyperthermia radiofrequency ablation system, an electrothermal coupled finite element model is established. The effects of the parameters such as hemoperfusion and water cooling temperature on the thermal damage during the whole heating process are emphatically discussed. It is concluded that the highest temperature region of the tissue is located at the 2-3mm on the electrode surface under water cooling, and the lower the water cooling temperature is, the larger the ablation range is. When the hemoperfusion rate of the tissue changed from 0 to 3. 0e-3 / s-1 / s, the diameter of the heat injury decreased by 33. 8%. The data showed that the hemoperfusion rate had a great influence on the temperature and the volume of the thermal injury. Two methods for determining thermal damage boundary (50 鈩，

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