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Int J Numer Method Biomed Eng. 2017 Nov;33(11). doi: 10.1002/cnm.2869. Epub 2017 Apr 7.

How coagulation zone size is underestimated in computer modeling of RF ablation by ignoring the cooling phase just after RF power is switched off.

Author information

1
Instituto de Física de Líquidos y Sistemas Biológicos (CONICET), Calle 59 No 789, B1900BTE, La Plata, Argentina.
2
Instituto de Ingeniería y Agronomía, Universidad Nacional Arturo Jauretche, Avenida Calchaquí No 6200, 1888, Florencio Varela, Argentina.
3
Instituto Universitario de Matemática Pura y Aplicada, Universitat Politècnica de València, Camí de Vera, 46022, València, Spain.
4
Biomedical Synergy, Electronic Engineering Department, Universitat Politècnica de València, Camí de Vera, 46022, València, Spain.

Abstract

All the numerical models developed for radiofrequency ablation so far have ignored the possible effect of the cooling phase (just after radiofrequency power is switched off) on the dimensions of the coagulation zone. Our objective was thus to quantify the differences in the minor radius of the coagulation zone computed by including and ignoring the cooling phase. We built models of RF tumor ablation with 2 needle-like electrodes: a dry electrode (5 mm long and 17G in diameter) with a constant temperature protocol (70°C) and a cooled electrode (30 mm long and 17G in diameter) with a protocol of impedance control. We observed that the computed coagulation zone dimensions were always underestimated when the cooling phase was ignored. The mean values of the differences computed along the electrode axis were always lower than 0.15 mm for the dry electrode and 1.5 mm for the cooled electrode, which implied a value lower than 5% of the minor radius of the coagulation zone (which was 3 mm for the dry electrode and 30 mm for the cooled electrode). The underestimation was found to be dependent on the tissue characteristics: being more marked for higher values of specific heat and blood perfusion and less marked for higher values of thermal conductivity.

KEYWORDS:

ablation; radiofrequency heating; tumor ablation

PMID:
28146314
DOI:
10.1002/cnm.2869
[Indexed for MEDLINE]

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