Clinical Study On Tissue Temperature Distribution In Percutaneous Microwave Liver Tumor Coagulation Treatment

Objective: To study tissue temperature distribution in the coagulation treatment of liver tumor induced through implanted microwave electrodes and to reveal factors that prevent tissue temperature from rising in the ablation treatment and to study the role of real-time temperature monitoring in the liver tumor coagulation treatment. Materials and Methods: From August 1999 to October 2001, 114 patients with a total of 146 hepatic tumors were treated with percutaneous microwave coagulation techniques in our department, and temperatures of 310 spots-times in the coagulation area were recorded. (1) Base on the recorded temperatures, thermal field of microwave radiation were studied and comparison between the clinically measured thermal field and the computer simulated thermal field were conducted. (2) Before treatment, in 45 patients, 62 tumors were classified into three groups base on tumors blood perfusion on color Doppler sonogram. There are 13 nodules with rich blood perfusion, 29 nodules with moderate blood perfusion and 20 nodules with poor blood perfusion. Tissue temperature rise during the coagulation treatment was compared between groups so as to clarify the influence of blood perfusion on thermal field. (3) After percutaneous microwave coagulation, follow-ups were conducted through ultrasonography, CT, MRI and post-treatment biopsy. Successful follow-ups were achieved in 51 patients with a total of 72nodules. The relationship between the temperatures in the tumors peripery during coagulation treatment and the tumors' complete necrosis were studied. Results: In the clinical tumor ablation treatment, temperature distribution is regular. Temperatures decrease with the increase of the distance from the microwave electrodes and the level of the temperature decrease was fitted with an exponential decay. Temperature distribution curve was well coincided with computer simulation curve under condition of 4.0kg/m3/s tissue blood perfusion. Temperature distribution showed that the average short axis diameter of the coagulated volume was 26.8mm with single electrode and 39.2?.llmm with double electrodes, and computer simulated coagulation volume is very close to this results. (2)tumors' blood perfusion significantly affects the temperature rise. Temperatures rise more efficiently in tumors with poor blood perfusion than in tumors with rich blood perfusion. Temperature distribution status in tumor with rich blood perfusion, moderate blood perfusion and poor blood perfusion was well coincided with computer simulation under condition of 7.0kg/m3/s> 4.0kg/m3/s and 1.5kg/m3/s tissue blood perfusion, respectively. (3) In the clinical treatment, temperature in the peripery of 72 nodules reached 46-78 癈 , average 56.3 ?.1 癈 (mean ?standard), and follow-up results show that 91.7% ( 66/72 ) were completely necrosis. Conclusion: A large number of spots-temperature measurements show that, in the clinical tumor coagulation treatment, temperature distribution is regular, and computer-aided simulation of microwave-induced thermal distribution model in coagulation of liver tumor is applicableto clinical tumor treatment. Blood perfusion and tumors capsule are the main factors that influence temperature distribution. Temperature change in the tumor peripery during the coagulation treatment can be used as an objective standard to predict the therapy effectiveness.