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《Chinese Journal of Uitrasonography》 2002-04
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Study on thermal field during ultrasound-guided implanted microwave coagulation in phantom

LIANG Ping *, DONG Baowei, YU Xiaoling,et al. *Department of Ultrasonography, Chinese PLA General Hospital, Beijing 100853, China  
Objective To investigate thermal distribution of implanted microwave coagulation in equivalent liver phantom.Methods In equivalent phantom test of the liver, it was available to pinpoint the spots of measurement and measure the temperature precisely. Such measurements were performed in 16 sites each time and at each site were repeated 5~9 times at the same power output level. Sixteen thermocouples were used to measure the transient temperature from which the specific absorption rate (SAR) values were determined. Based on Pennes formulation of thermal biology, the thermal model of implanted microwave hyperthmia for liver cancer was deduced. Thermal distributions were widely calculated and predicted by computer simulation with finite element model (FEM) under three power output (60 W 5 min, 50 W 10 min, and 40 W 30 min).Results The SAR distributions were determined in the liver equivalent phantom test. In the r direction, microwave thermal field was fitted with an exponential decay. In θ direction, it was fitted with cosine θ. In the z direction, it corresponded to a third order polynomial. Speed of temperature rise in z 0 direction was faster than that in z 0 direction. SAR distribution was different at different power output. There was no relationship between SAR values and power outputs. Based on SAR values, thermal fields were dynamically reconstructed with computer simulation.Conclusions Temperature distributions of microwave radiation are regular, which decay from central electrode to peripheral tissue. The temperature distribution can be reconstructed with computer simulation. Computer simulation can dynamically monitor the temperature rise on three dimensions. It provides a theoretical and technical basis for precisely controlling thermal fields during the microwave hyperthermia treatment of the liver cancer.
【Fund】: 国家自然科学基金项目 (39870 794)
【CateGory Index】: R73-36
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