[Fluid-modulated RF ablation: in-vitro experiments].
OBJECTIVE
To evaluate the potential of different fluids to enhance the effect of radiofrequency ablation.


METHODS
A bipolar radiofrequency system with an internally cooled needle electrode was used to heat three samples of 16 different fluids. Each sample had a volume of 20 ml. The generator output was set to 20 watt as recommended by the vendor. Energy was applied until the temperature of the sample reached 80 degrees C or the duration of heating exceeded 30 minutes. If a fluid was not able to be heated because the resistance was too high, 15 ml of the fluid were mixed with 5 ml of a 1-mol saline solution. During energy deposition, the temperature was measured every 15 seconds. The applied energy, impedance, resistance, voltage and flowing current were recorded continuously.


RESULTS
The ionic contrast agent Telebrix Gastro was heated to 80 degrees C within 620 +/- 95 seconds which was the shortest time needed. It was not possible to heat the contrast agents Solutrast 300, Isovist 240, Gadovist and Lipiodol as well as a 40 % glucose solution and 95 % ethanol. The longest time was needed to heat the 40 % glucose solution + the 1-mol saline solution (1755 +/- 26 seconds). The correlation coefficients (Pearson) showed only a marginal connection between resistance and maximum temperature (r=0.52) and duration for heating up to 80 degrees C, respectively (r=- 0.54). The same is true for the connection between impedance and maximum temperature (r=0.52) as well as duration for heating up to 80 degrees C (r=- 0.57).


CONCLUSIONS
The selection of an appropriate fluid allows an increase in the effect of radiofrequency ablation or the generation of a protective effect. Especially HAES, Magnevist and Telebrix Gastro are suitable for enhancing heating. Glucose solution or non-ionic contrast agents could be used to generate a protective effect during radiofrequency ablation. The heating of fluids by means of a bipolar radiofrequency ablation system is not only influenced by the electric properties but also by other parameters such as the specific heat capacity.
Bruners
P
P
Lehrstuhl für Angewandte Medizintechnik, Helmholtz-Institut für Biomedizinische Technik, Aachen. bruners@hia.rwth-aachen.de
Hodenius
M
M
Günther
R W
RW
Schmitz-Rode
T
T
Mahnken
A
A
D017115:Catheter Ablation / Q000379:methods*; D003287:Contrast Media; D006801:Humans; D008171:Lung Diseases / Q000628:therapy*; D011846:Radio Waves; D015203:Reproducibility of Results
D003287:Contrast Media