Finite Element Analysis of Hepatic Radiofrequency Ablation Probes using Temperature-Dependent Electrical Conductivity

BACKGROUND: Few finite element models (FEM) have been developed to describe the electric field, specific absorption rate (SAR), and the temperature distribution surrounding hepatic radiofrequency ablation probes. To date, a coupled finite element model that accounts for the temperature-dependent electrical conductivity changes has not been developed for ablation type devices. While it is widely acknowledged that accounting for temperature dependent phenomena may affect the outcome of these models, the effect has not been assessed. METHODS: The results of four finite element models are compared: constant electrical conductivity without tissue perfusion, temperature-dependent conductivity without tissue perfusion, constant electrical conductivity with tissue perfusion, and temperature-dependent conductivity with tissue perfusion. RESULTS: The data demonstrate that significant errors are generated when constant electrical conductivity is assumed in coupled electrical-heat transfer problems that operate at high temperatures. These errors appear to be closely related to the temperature at which the ablation device operates and not to the amount of power applied by the device or the state of tissue perfusion. CONCLUSION: Accounting for temperature-dependent phenomena may be critically important in the safe operation of radiofrequency ablation device that operate near 100°C

Revista de educación

Se intenta exponer, de una manera clara y sencilla, los problemas que implican la comprensión del proceso de aprendizaje, mediante el uso de estructuras matemáticas.Ministerio Educación CIDEBiblioteca de Educación del Ministerio de Educación, Cultura y Deporte; Calle San Agustín, 5 - 3 Planta; 28014 Madrid; Tel. +34917748000; [email protected]

Ernest Hemingway: A New Life

Biography geared to general readers, students, and scholars offering a balanced portrait of Hemingway’s life and evolving art through a variety of critical perspectives. Hutchisson covers all stages of Hemingway’s life and writings from Oak Park to Ketchum, focusing on the influence of wives, lovers, and geographic locale on his writing. Discusses Hemingway’s complex medical history and lifelong battle with depression, contending that the author’s medical condition contributed more than anything else to his suicide. Draws on manuscripts, correspondence, family histories, medical records, and other archived material. Includes over twenty black-and-white photographs along with extensive endnotes and index