Silicon Carbide-Enhanced Microwave Ablation in an Ex-Vivo Bovine Liver Model – Effects on Heat Distribution and Ablation Volume

Abstract

Purpose: Evaluation of the maximum temperatures and ablation volumes in microwave ablation (MWA) after injection of different concentrations of silicon carbide (SiC) particles in an ex-vivo bovine liver model.

Materials and Methods: 15 ml of different concentrations of SiC particles (20 vol% SiC; 50 vol% SiC) mixed with 2 % gelatin were injected into an ex-vivo bovine liver. As a reference group, 2 % gelatin without SiC was injected. MWA was performed using a clinical MWA system with different generator settings (10 – 45 W/10 minutes). The temperature was measured at a distance of 5 mm and 10 mm from the applicator. Afterwards the liver tissue was sliced along the short and long axis, the ablation zones were measured on the x, y and z-axis and the ablation volume was calculated. All experiments were performed 5 times (total: 40 experiments).

Results: The average maximum temperatures measured at a generator setting of 45 W at a distance of 5 mm from the applicator were 103.4 ± 4.6 °C (20 vol% SiC), 103.3 ± 6.5 °C (50 vol% SiC) and 96.0 ± 4.2 °C in the control group (0 vol% SiC). At 45 W, injection of 20 vol% SIC caused a significantly higher maximum temperature than that achieved in the control group (p = 0.016). No significant temperature increase compared to the control group could be measured using 50 vol% SiC. The mean ablation volumes at 45 W and 20 vol% SiC and 50 vol% SiC were significantly larger (172.7 ± 31.5 ml and 171.0 ± 34.7 ml, respectively) than those achieved in the control group (111.2 ± 23.8 ml) (p = 0.027 and p = 0.045).

Conclusion: In an ex-vivo bovine liver model, the SiC particles demonstrated an enhancing effect of MWA with respect to maximum temperatures and ablation volume. Therefore, SiC is a promising candidate for enhancing MWA in vivo.

Zusammenfassung

Ziel: Untersuchung der Maximaltemperaturen und der Ablationsvolumina bei der Mikrowellenablation (MWA) nach Injektion verschiedener Konzentrationen von Siliciumcarbid (SiC) in einem ex-vivo-Rinderlebermodell.

Material und Methoden: 15 ml unterschiedlicher Mengen SiC-Partikel gemischt mit 2 % Gelatine (20 Vol% SiC; 50 Vol% SiC) wurden in Rinderleber injiziert. Als Kontrollgruppe wurde 2 % Gelatine ohne SiC verwendet. Die MWA wurde mit einem klinisch zugelassenen MWA-System mit verschiedenen Generatoreinstellungen (10 – 45 W/10 min) durchgeführt. Die Temperatur wurde dabei in 5 mm und 10 mm Abstand zum Applikator gemessen. Anschließend wurde jeweils das Ablationsareal exzidiert, entlang der x-, y- und z-Achse vermessen und das Ablationsvolumen berechnet. Alle Versuche wurden 5-fach durchgeführt.

Ergebnisse: Die durchschnittlichen Maximaltemperaturen mit 45 W Generatorleistung in 5 mm Abstand zum Applikator betragen 103,4 ± 4,6 °C (20 Vol% SiC), 103,3 ± 6,5 °C (50 Vol% SiC) und 96,0 ± 4,2 °C (Kontrollgruppe). Bei 45 W ist die Maximaltemperatur durch Hinzugabe von 20 Vol% SiC signifikant höher als in der Kontrollgruppe (p = 0,016). Keine signifikanten Unterschiede im Vergleich zur Kontrollgruppe sind bei der Verwendung von 50 Vol% SiC zu beobachten. Das Ablationsvolumen ist bei Verwendung von 20 Vol% und 50 Vol% SiC (172,7 ± 31,5 ml and 171,0 ± 34,7 ml) signifikant größer als in der Kontrollgruppe (111,2 ± 23,8 ml) (p = 0,027 und p = 0,045).

Schlussfolgerung: In einem ex-vivo-Rinderlebermodell konnten durch die Injektion verschiedener SiC-Gelatine-Mischungen verstärkende Effekte hinsichtlich Maximaltemperatur und Ablationsvolumen demonstriert werden. Aus diesem Grund ist SiC ein vielversprechender Kandidat zur in-vivo-Anwendung.

Key words

technical aspects - ablation procedures - experimental study

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