In vivo study of the temperature changes of brain tissue surrounding microwave ablation zone in ;a canine model / 中华医学超声杂志（电子版）

ABSTRACT

Objective To investigate the alteration of peripheral tissue`s temperature of the coagulation zone of microwave ablation in brain tissue, and to provide experimental evidence for clinical application. Methods Twelve canines were treated by microwave ablation in brain tissue. Each was ablated for 180 s with microwave output power of 20 W, 30 W, and 40 W. During the operation the peripheral temperature at the distance of 0.5 cm, 1.0 cm, 1.5 cm and 2.0 cm from the ablation center was recorded respectively. The ultrasound was performed 1 hour after the operation, and then the animals were executed and the microscopic changes of the ablation lesion were observed. Results Eleven canines suffered well for the ablation, while 1 presented abnormal respiration during the operation and died 2 hours later. During the operation, the temperature of the area 0.5 cm from the center rose signiifcantly, with the maximum temperature was (96.40±1.46)℃at the power of 20 W, and 100℃at the power of 30 W and 40 W. The temperature of the area 1.0 cm from the center rose faster, with the maximum temperatures at different powers all above the 46℃. The temperature of the area 1.5 cm from the center rose slower, with the maximum temperature below 46℃at the power of 20 W and 30 W and above 46℃at the power of 40 W. The maximum temperatures of the area 2.0 cm from the center at different powers were all below 46℃. The difference of the maximum temperature at different distances (1.0 cm, 1.5 cm, and 2.0 cm from the center) was signiifcant (F=776.78, 2640.64 and 3025.53, all P<0.05). The length and width of the ablation lesion as well as the area of edema increased with the power. At the power of 20 W, 30 W, and 40 W, the length of the ablation lesion was (29.3±1.8) mm, (32.7±2.1) mm and (34.2±2.4) mm, the width was (22.5±1.5) mm, (23.7±1.7) mm and (27.1±2.0) mm, and the width of the edema zone was (2.3±0.4) mm, (2.6±0.4) mm and (2.7±0.5) mm. The differences of the length and width of the ablation lesion at different powers were signiifcant (F=11.46, 14.49, both P<0.01). The difference of the edema area at different powers was insigniifcant (F=1.94, P=0.169). Conclusions Microwave ablation is a safe therapeutic modality. However, the shorter distance from the ablation center and greater ablation power give rise to larger ablation lesion, higher maximum temperature, and faster temperature increase. Therefore, 2.0 cm from the ablation center is a safe area.