How large is the periablational zone after radiofrequency and microwave ablation? Computer-based comparative study of two currently used clinical devices

Figures

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  Figure 1.. (a) Moderate hyperthermic heating occurs in periablational zone and has been related with tumor cell activity [1]. This heating could affect either a tumor area outside the thermal coagulation zone (which is completely destroyed) or nearby micronodules. (b) Relation between percentage of living cells after heating and index Ω obtained from the Arrhenius damage model, which associates temperature with exposure time using a first-order kinetics relationship. Periablational zone was assumed to be between Ω=0.6 and Ω=2.1 (values derived from experimental data in [1], see text for details), while coagulation zone was defined by the Ω=4.6 contour, which represents 99% probability of cell death.

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  Figure 2.. Temperature distributions computed from RFA(Cool-tip applicator, pulsed protocol, 10 min) and MWA (Amica-Gen applicator, 60 W continuous application, 10 min) just after switch-off (a) and 10 min later (b). White lines represent limits of coagulation zone (Ω>4.6) and periablational zones (0.6 < Ω < 2.1). (Scale in °C; MWA temperatures exceeded 110 °C).

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  Figure 3.. Coagulation and periablational zone volumes in RFA/MWA simulations. Lighter color bars and bottom values are the volumes computed just after switch-off. Darker color bars represent the increase in volume 10 min after switch-off. Upper values give total volumes after this 10-min period.

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  Figure 4.. Periablational/coagulation volume ratios in RFA/MWA simulations. Lighter color bars and bottom values are the ratios computed just after switch-off. Darker color bars represent the increased ratio 10 min after switch-off. Upper values show the ratio after this 10-min period.

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  Figure 5.. Overlapping coagulation zones after 10 min of RFA (~51 W) and MWA (60 W). Note that while the volumes offer similar values, the MWA transverse diameter is larger.