Curto Sergio, Taj-Eldin Mohammed, Fairchild Dillon, Prakash Punit
Department of Electrical and Computer Engineering, Kansas State University, Manhattan, Kansas 66506.
Med Phys. 2015 Nov;42(11):6152-61. doi: 10.1118/1.4931959.
The relationship between microwave ablation system operating frequency and ablation performance is not currently well understood. The objective of this study was to comparatively assess the differences in microwave ablation at 915 MHz and 2.45 GHz.
Analytical expressions for electromagnetic radiation from point sources were used to compare power deposition at the two frequencies of interest. A 3D electromagnetic-thermal bioheat transfer solver was implemented with the finite element method to characterize power deposition and thermal ablation with asymmetrical insulated dipole antennas (single-antenna and dual-antenna synchronous arrays). Simulation results were validated against experiments in ex vivo tissue.
Theoretical, computational, and experimental results indicated greater power deposition and larger diameter ablation zones when using a single insulated microwave antenna at 2.45 GHz; experimentally, 32±4.1 mm and 36.3±1.0 mm for 5 and 10 min, respectively, at 2.45 GHz, compared to 24±1.7 mm and 29.5±0.6 mm at 915 MHz, with 30 W forward power at the antenna input port. In experiments, faster heating was observed at locations 5 mm (0.91 vs 0.49 °C/s) and 10 mm (0.28 vs 0.15 °C/s) from the antenna operating at 2.45 GHz. Larger ablation zones were observed with dual-antenna arrays at 2.45 GHz; however, the differences were less pronounced than for single antennas.
Single- and dual-antenna arrays systems operating at 2.45 GHz yield larger ablation zone due to greater power deposition in proximity to the antenna, as well as greater role of thermal conduction.
目前对微波消融系统工作频率与消融性能之间的关系了解尚不充分。本研究的目的是比较评估915兆赫兹和2.45吉赫兹微波消融的差异。
采用点源电磁辐射的解析表达式来比较两个感兴趣频率下的功率沉积。利用有限元方法实现了一个三维电磁热生物热传递求解器，以表征非对称绝缘偶极天线（单天线和双天线同步阵列）的功率沉积和热消融。模拟结果通过离体组织实验进行验证。
理论、计算和实验结果表明，使用2.45吉赫兹的单根绝缘微波天线时，功率沉积更大，消融区直径更大；在实验中，2.45吉赫兹下5分钟和10分钟时消融区直径分别为32±4.1毫米和36.3±1.0毫米，而915兆赫兹下分别为24±1.7毫米和29.5±0.6毫米，天线输入端口的前向功率为30瓦。在实验中，在距离2.45吉赫兹工作天线5毫米（0.91对0.49℃/秒）和10毫米（0.28对0.15℃/秒）处观察到更快的加热速度。2.45吉赫兹下双天线阵列的消融区更大；然而，差异不如单天线明显。
工作在2.45吉赫兹的单天线和双天线阵列系统由于天线附近更大的功率沉积以及热传导的更大作用，产生更大的消融区。
