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Int J Hyperthermia. 2016 May;32(3):221-30. doi: 10.3109/02656736.2015.1135998. Epub 2016 Feb 10.

Computer modelling of RF ablation in cortical osteoid osteoma: Assessment of the insulating effect of the reactive zone.

Author information

1
a Instituto de Física de Líquidos y Sistemas Biológicos (CONICET) , La Plata , Argentina .
2
b Instituto de Ingeniería y Agronomía, Universidad Nacional Arturo Jauretche , Argentina .
3
c Instituto Universitario de Matemática Pura y Aplicada, Universitat Politècnica de València , Spain .
4
d Radiodiagnostic Department, Hospital Universitario Fundación Alcorcón , Madrid , Spain , and.
5
e Biomedical Synergy, Electronic Engineering Department, Universitat Politècnica de València , Spain.

Abstract

PURPOSE:

The aim was to study by computer simulations the insulating role of the reactive zone surrounding a cortical osteoid osteoma (OO) in terms of electrical and thermal performance during radiofrequency ablation (RFA).

MATERIAL AND METHODS:

We modelled a cortical OO consisting of a nidus (10 mm diameter) enclosed by a reactive zone. The OO was near a layer of cortical bone 1.5 mm thick. Trabecular bone partially surrounds the OO and there was muscle around the cortical bone layer. We modelled RF ablations with a non-cooled-tip 17-gauge needle electrode (300 s duration and 90 °C target temperature). Sensitivity analyses were conducted assuming a reactive zone electrical conductivity value (σrz) within the limits of the cortical and trabecular bone, i.e. 0.02 S/m and 0.087 S/m, respectively. In this way we were really modelling the different degrees of osteosclerosis associated with the reactive zone.

RESULTS:

The presence of the reactive zone drastically reduced the maximum temperature reached outside it. The temperature drop was proportional to the thickness of the reactive zone: from 68 °C when it was absent to 44 °C when it is 7.5 mm thick. Higher nidus conductivity values (σn) implied higher temperatures, while lower temperatures meant higher σrz values. Changing σrz from 0.02 S/m to 0.087 S/m reduced lesion diameters from 2.4 cm to 1.8 cm.

CONCLUSIONS:

The computer results suggest that the reactive zone plays the role of insulator in terms of reducing the temperature in the surrounding area.

KEYWORDS:

Computer modelling; cortical bone; finite element method; osteoid osteoma; radiofrequency ablation; reactive zone

PMID:
26862788
DOI:
10.3109/02656736.2015.1135998
[Indexed for MEDLINE]
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