Microwave Recanalization: Thermal Effects with Nitinol and Stainless-Steel Stents

Background and Study Aims: A previous study we conducted evaluated the thermal effects of microwave irradiation when attempting recanalization of a nitinol stent occluded by tumor ingrowth. The present study evaluates the thermal effects of microwave irradiation on different stents in vitro.

Methods: The thermal response to microwave energy was evaluated in a muscle-equivalent phantom containing a nitinol (Accuflex) or stainless-steel stent (Wallstent). The phantom temperature was monitored continuously at different distances from an electrode, with either stent type in place. The tip of the electrode was either in contact with the stent or not in contact with it.

Results: The steel stent showed a smaller temperature increase than nitinol at 2 mm from the electrode. Without electrode contact, the stents did not differ significantly during the first 40 s of irradiation. The stents did not differ significantly with regard to temperatures further from the electrode. When the electrode was in contact with the stent, the rise in temperature was significantly greater with the stainless-steel stent than with the nitinol one, but the phantom temperature did not exceed 45 °C with either of the stents.

Conclusions: In patients with a Wallstent stainless-steel stent, microwave coagulation therapy to recanalize stent occlusions appears to be feasible in the same conditions as with an Accuflex nitinol stent.

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