Theoretical comparison of intraluminal heating techniques

Abstract

Introduction: This study compared simulated temperature distributions of intraluminal heating devices, concerning penetration and homogeneity. A hot water balloon, a 434-MHz monopole and a 915-MHz dipole antenna, both with incorporated cooling, and a 27-MHz applicator were investigated. Methods: The hot water balloon had an inlet temperature of 45 degrees C and a flow rate of 7.85 mls(-1). The cooling water and air had a temperature of 41 degrees C and 37 degrees C and a flow rate of 5.89 mls(-1) and 1.81s(-1), respectively. A 27-MHz applicator consisting of one or two electrode(s) was modelled to demonstrate axial steering for inhomogeneous tissue properties. Calculated power distributions were scaled to a total power of 10W in tissue before the corresponding temperature distributions were calculated. Results: The hot water balloon and the 27-MHz device showed a thermal penetration depth of similar to 4 and similar to 10 mm, respectively. The penetration depths of the 434- and 915-MHz applicators were comparable: similar to 10 and similar to 16mm with water and air cooling, respectively. With the 27-MHz applicator, spatial steering was applied to minimize temperature gradients along the applicator. The 434- and 915-MHz antennas have no steering possibilities. The temperature distribution of the hot water balloon is not affected by inhomogeneous dielectric properties, only slightly by inhomogeneous perfusion. Conclusion: A hot water balloon is useful for heating tumours with a limited infiltration in tissue, while a 27-MHz device has the best potential to realize a homogeneous temperature distribution in larger tumours.