title: Computer modelling of RF ablation in cortical osteoid osteoma: Assessment of the insulating effect of the reactive zone.
abstract: 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).
  
  
  
  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.
  
  
  
  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.
  
  
  
  The computer results suggest that the reactive zone plays the role of insulator in terms of reducing the temperature in the surrounding area.
authors: a Instituto de Física de Líquidos y Sistemas Biológicos (CONICET) , La Plata , Argentina .|b Instituto de Ingeniería y Agronomía, Universidad Nacional Arturo Jauretche , Argentina .
authors: Ramiro M
authors: RM
authors: Irastorza
authors: c Instituto Universitario de Matemática Pura y Aplicada, Universitat Politècnica de València , Spain .
authors: Macarena
authors: M
authors: Trujillo
authors: d Radiodiagnostic Department, Hospital Universitario Fundación Alcorcón , Madrid , Spain , and.
authors: Jose
authors: J
authors: Martel Villagrán
authors: e Biomedical Synergy, Electronic Engineering Department, Universitat Politècnica de València , Spain.
authors: Enrique
authors: E
authors: Berjano
mesh_terms: D001859:Bone Neoplasms / Q000601:surgery*; D017115:Catheter Ablation; D003198:Computer Simulation; D000071538:Cortical Bone / Q000502:physiology; D004553:Electric Conductivity; D004566:Electrodes; D008954:Models, Biological; D010017:Osteoma, Osteoid / Q000601:surgery*; D013696:Temperature; D013814:Thermal Conductivity
keywords: Computer modelling; cortical bone; finite element method; osteoid osteoma; radiofrequency ablation; reactive zone