Ramiro M Irastorza1,2, Macarena Trujillo3, Jose Martel Villagrán4, Enrique Berjano5. 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.
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.
Entities:
Keywords:
Computer modelling; cortical bone; finite element method; osteoid osteoma; radiofrequency ablation; reactive zone
Authors: Ricardo Rivas; Rudy B Hijlkema; Ludo J Cornelissen; Thomas C Kwee; Paul C Jutte; Peter M A van Ooijen Journal: Int J Numer Method Biomed Eng Date: 2021-08-08 Impact factor: 2.648