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

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

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bone Neoplasms / surgery*
  • Catheter Ablation*
  • Computer Simulation
  • Cortical Bone / physiology
  • Electric Conductivity
  • Electrodes
  • Models, Biological*
  • Osteoma, Osteoid / surgery*
  • Temperature
  • Thermal Conductivity