Conformal coverage of liver tumors by the thermal coagulation zone in 2450-MHz microwave ablation

Abstract

Purpose: To optimize treatment schemes using 2450-MHz microwave ablation (MWA), a novel conformal coverage method based on bipolar-angle mapping is proposed that determines whether a liver tumor is completely encompassed by thermal coagulation zones. Materials and methods: Firstly, three-dimensional (3-D) triangular mesh data of liver tumors were reconstructed from clinical computed tomography (CT) slices using the Marching cubes (MC) algorithm. Secondly, characterization models of thermal coagulation zones were established based on finite element simulation results of 40, 45, 50, 55, and 60 W ablations. Finally, coagulation zone models and tumor surface data were mapped and fused on a two-dimensional (2-D) plane to achieve conformal coverage of liver tumors by comparing the corresponding polar radii. Results: Optimal parameters for ablation treatment of liver tumors were efficiently obtained with the proposed conformal coverage method. Fifteen liver tumors were obtained with maximal diameters of 12.329-78.612 mm (mean ± standard deviation, 39.094 ± 19.447 mm). The insertion positions and orientations of the MWA antenna were determined based on 3-D reconstruction results of these tumors. The ablation patterns and durations of tumors were planned according to the minimum mean standard deviations between the ablative margin and tumor surface. Conclusion: The proposed method can be applied to computer-assisted MWA treatment planning of liver tumors, and is expected to guide clinical procedures in future.

A review of antenna designs for percutaneous microwave ablation

“…There exist both omni-directional and directional radiation pattern approaches for delivery of the microwave energy in literature. As for omni-directional antennas, energy can be transferred into tissues in all directions around the antenna, which was usually used to eradicate tumors in a regular shape (e.g., spherical or elliptical) [21][22][23]. On the other hand, a directional antenna that affords spatial control of the energy deposition may be a better choice when tumors are in proximity to critical structures, such as blood vessels or bile ducts.…”

Thermal ablation of biological tissues in disease treatment: A review of computational models and future directions

“…Alternative to the experimental validation based on ablation zone quantification, studies have also been reported on the comparison between the spatio-temporal temperature distribution utilizing an array of thermocouples, thermistors or fibre-optic based sensors around the applicator. Importantly, there has been tremendous research focus on developing thermometric (both invasive and non-invasive) techniques for real-time visualization/monitoring of the tissue temperature and ablation volume during thermal ablative procedures (Eyerly et al, 2015, Almekkawy et al, 2019, Gao et al, 2019c, Quirk and Lu, 2019. However, special care should be taken to address the mechanical deformation induced by the elevated temperatures during the thermal ablative procedures.…”

Influences of blood flow parameters on temperature distribution during liver tumor microwave ablation

“…The specific heat capacity function based on the change of water content is as follows [26][27][28]:…”