Open AccessElectric and Thermal Field Effects in Tissue Around Radiofrequency Electrodes
Author(s) -
Cosman Eric R.,
Cosman Eric R.
Publication year - 2005
Publication title -
pain medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.893
H-Index - 97
eISSN - 1526-4637
pISSN - 1526-2375
DOI - 10.1111/j.1526-4637.2005.00076.x
Subject(s) - materials science , electric field , electrode , radio frequency , thermocouple , rf probe , signal (programming language) , biomedical engineering , finite element method , thermal , dielectric heating , nuclear magnetic resonance , mechanics , acoustics , rf power amplifier , composite material , optoelectronics , chemistry , electrical engineering , physics , medicine , dielectric , thermodynamics , amplifier , cmos , quantum mechanics , computer science , programming language , engineering
Objective. A study is carried out of the spatial distribution and time dependence of electric and thermal fields in the tissue around a radiofrequency (RF) electrode used in pain therapy. Finite‐element calculation of the fields is performed, and results are compared with ex vivo tissue data. Field predictions are made for continuous and for pulsed RF applications. Design. A special RF cannula electrode is constructed with both macro and micro thermocouple sensors to measure both average and rapid, transitory temperature effects. Temperatures and impedances are recorded in liver and egg‐white models using signal outputs from a commercially available RF lesion generator. These data are compared with the results of finite‐element calculations using electric field equations and the bio‐heat equation. Results. Average and pulsatory temperatures at the RF electrode are measured. Rapid temperature spikes during pulsed RF bursts are observed. These data compared well with theoretical calculations using known electrical and thermal tissue parameters. Conclusion. Continuous RF lesioning causes heat destruction of neurons. Pulsed RF lesioning (PRFL) produces heat bursts with temperatures in the range associated with destructive heat lesions. PRFL also produces very high electric fields that may be capable of disrupting neuronal membranes and function. Finite‐element calculations agree substantially with the measured data, giving confidence to their predictions of fields around the RF electrode.