Multipolar radiofrequency ablation using internally cooled electrodes in ex vivo bovine liver: correlation between volume of coagulation and amount of applied energy.
OBJECTIVE
To evaluate the relationship between applied energy and volume of coagulation induced by multipolar radiofrequency (RF) ablation.


METHODS
Multipolar RF ablations (n=80) were performed in ex vivo bovine liver. Three bipolar applicators with two electrodes located on each applicator shaft were placed in a triangular array. The power-output (75-225 W) and the distance between the different applicators (2, 3, 4, 5 cm) were systematically varied. The volume of confluent white coagulation and the amount of applied energy were assessed. Based on our experimental data the relationship between the volume of coagulation and applied energy was assessed by nonlinear regression analysis. The variability explained by the model was determined by the parameter r(2).


RESULTS
The volume of coagulation increases with higher amounts of applied energy. The maximum amount of energy was applied at a power-output of 75 W and an applicator distance of 5 cm. The corresponding maximum volume of coagulation was 324 cm(3) and required an application of 453 kJ. The relationship between amount of applied energy (E) and volume (V) of coagulation can be described by the function, V=4.39E(0.7) (r(2)=0.88). By approximation the volume of coagulation can be calculated by the linear function V=0.61E+40.7 (r(2)=0.87).


CONCLUSIONS
Ex vivo the relationship between volume of coagulation and amount of applied energy can be described by mathematical modeling. The amount of applied energy correlates to the volume of coagulation and may be a useful parameter to monitor multipolar RF ablation.
University Hospital, Department of Diagnostic and Interventional Radiology, Hoppe-Seyler Str. 3, 72076 Tübingen, Germany. stephan.clasen@med.uni-tuebingen.de
Stephan
S
Clasen
Hansjörg
H
Rempp
Diethard
D
Schmidt
Christina
C
Schraml
Rüdiger
R
Hoffmann
Claus D
CD
Claussen
Philippe L
PL
Pereira
D000818:Animals; D001777:Blood Coagulation / Q000502:physiology / Q000528:radiation effects; D017115:Catheter Ablation / Q000295:instrumentation* / Q000379:methods*; D002417:Cattle; D003080:Cold Temperature; D004566:Electrodes; D006498:Hepatectomy / Q000295:instrumentation* / Q000379:methods*; D066298:In Vitro Techniques; D008099:Liver / Q000473:pathology* / Q000601:surgery*; D000078702:Radiofrequency Therapy; D013223:Statistics as Topic