Temperature gradient and elasticity gradient over the microwave-heated region in porcine liver in vitro

Abstract

Objective To explore the characteristics of changes in temperature and stiffness within the microwave-induced ablation region.Methods A type of Thy-ablation microwave antenna was used upon a design of various combination of ablation duration and power to induce heated region in samples of fresh porcine liver.Three special sites were set to assess the corresponding temperature and stiffness in each heated region.The temperature was continuously measured by using electronic thermometer with microwave on going,while stiffness was determined 5min after the ending of ablation by using real-time ultrasonic elastography,strain ratio,a quantitative indicator.Results The SR values and temperature determinations decreased progressively from the central to the peripheral area of the heated region.There was a linear regression between the temperatures (X) and SRs (Y),with Y =0.666 X-37.17.A significant correlation exists between X and Y,with the correlation coefficient being 0.956(P ＜0.001).The stiffness and temperature at the central sites are variable with the changes of both ablation time and power,but little changed at the peripheral sites of heated-region,which we name a phenomenon due to the ending effect of microwave propagation.Conclusions Temperature and stiffness increase considerably following microwave radiation but they are heterogeneously distributed within the ablated region in porcine liver.The characteristic gradient changes are confirmed of both temperature and the elasticity.It is presumable that good recognition and understanding and full utilization of these characteristics are conducive to reasonable control of tumor microwave ablation therapy. Key words: Ultrasonography; Microwaves/therapeutic use; Liver; Elasticity; Temperature