Macarena Trujillo1, Jose Bon2, María José Rivera3, Fernando Burdío4, Enrique Berjano5. 1. a Instituto Universitario de Matemática Pura y Aplicada, Universitat Politècnica de València , Spain. 2. b Food Technology Department , Universitat Politècnica de València , Spain. 3. c Applied Mathematics Department , Universitat Politècnica de València , Spain. 4. d Department of Surgery , Hospital del Mar , Barcelona , Spain. 5. e Biomedical Synergy, Department of Electronic Engineering , Universitat Politècnica de València , Spain.
Abstract
PURPOSE: To develop computer models to mimic the impedance-controlled pulsing protocol implemented in radiofrequency (RF) generators used for clinical practice of radiofrequency ablation (RFA), and to assess the appropriateness of the models by comparing the computer results with those obtained in previous experimental studies. METHODS: A 12-min RFA was modelled using a cooled electrode (17G, 3 cm tip) inserted in hepatic tissue. The short (transverse) diameter of the coagulation zone was assessed under in vivo (with blood perfusion (BP) and considering clamping) and ex vivo (at 21 °C) conditions. The computer results obtained by programming voltage pulses were compared with current pulses. RESULTS: The differences between voltage and current pulses were noticeable: using current instead of voltage allows larger coagulation zones to be created, due to the higher energy applied by current pulses. If voltage pulses are employed the model can accurately predict the number of roll-offs, although the waveform of the applied power is clearly not realistic. If current voltages are employed, the applied power waveform matches well with those reported experimentally, but there are significantly fewer roll-offs. Our computer results were overall into the ranges of experimental ones. CONCLUSIONS: The proposed models reproduce reasonably well the electrical-thermal performance and coagulation zone size obtained during an impedance-controlled pulsing protocol.
PURPOSE: To develop computer models to mimic the impedance-controlled pulsing protocol implemented in radiofrequency (RF) generators used for clinical practice of radiofrequency ablation (RFA), and to assess the appropriateness of the models by comparing the computer results with those obtained in previous experimental studies. METHODS: A 12-min RFA was modelled using a cooled electrode (17G, 3 cm tip) inserted in hepatic tissue. The short (transverse) diameter of the coagulation zone was assessed under in vivo (with blood perfusion (BP) and considering clamping) and ex vivo (at 21 °C) conditions. The computer results obtained by programming voltage pulses were compared with current pulses. RESULTS: The differences between voltage and current pulses were noticeable: using current instead of voltage allows larger coagulation zones to be created, due to the higher energy applied by current pulses. If voltage pulses are employed the model can accurately predict the number of roll-offs, although the waveform of the applied power is clearly not realistic. If current voltages are employed, the applied power waveform matches well with those reported experimentally, but there are significantly fewer roll-offs. Our computer results were overall into the ranges of experimental ones. CONCLUSIONS: The proposed models reproduce reasonably well the electrical-thermal performance and coagulation zone size obtained during an impedance-controlled pulsing protocol.