Forms of Energy Delivery during Cryo-cooled Radiofrequency Ablation for Optimization of the Ablation Result

Abstract

Purpose: Energy transfer from radiofrequency (RF) applicator to tissue is both precondition and limiting factor. The purpose of this ex vivo study was to examine the influence of form of energy delivery on ablation result during RF ablation with cryo-cooled applicators.

Materials and Methods: One hundred eight ablations were performed in ex vivo bovine liver under continuous energy delivery (A), pulsed energy delivery with reduced current during ablation pause (B) and impedance-dependent energy delivery. Maximum ablation time was 20 min. Early termination of ablation in case of loss of conductivity. Optimal ablation parameters were assessed. Short axis diameter of the ablation zone and ablation duration were determined. Ablation results under mode A, B and C were compared with analysis of variance and Tukey-Kramer HSD test. Influence of ablation duration on short axis diameter was evaluated with regression analysis.

Results: Significantly largest short axis diameter (51.1 mm ± SD 2.3; p = 0.01) was reached with impedance-dependent energy delivery (pulsed: 46.1 mm ± SD 5.6; continuous: 44.4 mm ± SD 4.1). Significantly longest ablation duration (1061.6 s ± SD 42.4; p = 0.01) was reached with impedance-dependent energy delivery (pulsed: 815.7 s ± 41.3; continuous: 715.3 s ± SD 82.2). Linear correlation between ablation duration and short axis diameter was calculated (R = 0.7).

Conclusion: Modification of energy delivery during RF ablation with cryo-cooled applicators improves energy transfer to tissue and enables larger ablation zones.

Key Points:

• Impedance-dependent energy delivery prevents early termination in kryo-based RF-ablation,

• Impedance-dependent energy delivery enables larger ablation zones than continuous energy delivery,

• Reduced current during ablation pause does not improve ablation results.

Citation Format:

• Hoffmann R, Bustamante J, Pitsaer C et al. Forms of Energy Delivery during Cryo-cooled Radiofrequency Ablation for Optimization of the Ablation Result. Fortschr Röntgenstr 2014; 186: 945 – 950

Zusammenfassung

Ziel: Der Energietransfer von Radiofrequenzsonden (RF-Sonden) auf das Zielgewebe ist Voraussetzung und limitierender Faktor der RF-Ablation. Ziel dieser Ex-vivo-Studie ist die Untersuchung des Einflusses der Form der Energieabgabe auf das Ablationsergebnis während RF-Ablation mit kryogekühlten Sonden.

Material und Methoden: Insgesamt 108 Ablationen wurden unter kontinuierlicher Energieabgabe (A), gepulster Energieabgabe mit reduzierten Ablationsströmen während Ablationspausen (B) und impedanzabhängiger (C) Energieabgabe an ex vivo Rinderlebern durchgeführt. Die Ablationszeit betrug maximal 20 min. Ggf. vorzeitiger Abbruch der Ablation bei Verlust der Gewebeleitfähigkeit. Optimale Ablationsparameter wurden ermittelt. Der Kurzachsendurchmesser der Ablationszone und die erreichte Ablationszeit wurden ermittelt. Der Vergleich der unter Ablationsmodi A, B und C erreichten Ergebnisse erfolgte mittels Varianzanalyse und Tukey-Kramer HSD-Test. Der Einfluss der Ablationszeit auf den Kurzachsendurchmesser wurde mit Regressionsanalyse untersucht.

Ergebnisse: Der signifikant größte Kurzachsendurchmesser (51,1 mm ± SD 2,3; p = 0,01) wurde unter impedanzabhängiger Energieabgabe erreicht (gepulst: 46,1 mm ± SD 5,6; kontinuierlich: 44,4 mm ± SD 4,1). Die signifikant längste mittlere Ablationszeit (1061,6 s ± SD 42,4; p = 0,01) wurde unter impedanzabhängiger Energieabgabe erreicht (gepulst: 815,7 s ± 41,3; kontinuierlich: 715,3 s ± SD 82,2). Eine lineare Korrelation zwischen Ablationszeit und Kurzachsendurchmesser wurde ermittelt (R = 0,70).

Schlussfolgerung: Durch Modifikation der Energieabgabe während RF-Ablation mit kryogekühlten Sonden lassen sich die Energieübertragung auf das Gewebe verbessern und größere Ablationszonen erzielen.

Key words

ablation procedures - experimental study - radiofrequency (RF) ablation - technical aspects

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