Abstract
The purpose of this study is to report how ex vivo model temperature can influence ablation zone dimensional performance claims. In this study, 72 microwave ablations were created in freshly harvested bovine livers using the Emprint™ ablation system at the 100 Watt generator setting. Bovine livers were submersed in a calibrated temperature controlled water bath prior to ablation testing to enable tight control (±2°C) of model background temperature across three model temperature groups (17°C, 25°C, 35°C). Within the 17°C liver model, ablations were performed for 60, 210, 510, 600, 900 and 1200 seconds. Within the 25°C liver model, ablations were performed for 300 and 600 seconds. Within the 35°C liver model, ablations were performed for 120, 240, 360 and 600 seconds. Immediately upon completion of each ablation sample, the ablation probe was removed and the ablation zone was bisected along the needle path. The ablation zone along the needle shaft (height) and in the cross-needle axis (width) was then grossly measured. Ablation zone cross-sections were photographed and data was statistically analyzed across temperature groupings. Within the 600 second ablation time grouping, the mean ablation width was 4.23 cm (17°C) vs 4.67 cm (25°C) vs 5.03 cm (35°C) (p<0.001), the mean ablation height was 4.15 cm (17°C) vs 4.50 cm (25°C) vs 4.75 cm (35°C) (p = 0.002), the mean ablation shape metric (minimum dimension/maximum dimension, 1.0 = sphere) was 0.96 (17°C) vs 0.96 (25°C) vs 0.93 (35°C) (p = 0.278), and the mean ablation volume (using ellipsoidal calculation) was 39.25 ml (17°C) vs 51.39 ml (25°C) vs 63.25 ml (35°C) (p<0.001). Ex-vivo background liver model temperature is a significant factor in microwave ablation dimensional performance. This study demonstrated a 61% increase in ablation volume by increasing model temperature from 17°C to 35°C. Manufacturers of microwave ablation systems utilize different model temperatures. When comparing ablation dimensional performance across microwave ablation systems, the model temperature used by each manufacturer is an important consideration.Tabled 1100 W Ablation Zone Dimension ResultsModel Temperature (ºC)Ablation Time (sec)NMean Ablation Diameter (cm)St Dev Ablation Diameter (cm)Mean Ablation Length (cm)St Dev Ablation Length (cm)Mean Ablation Volume (ml)St Dev Ablation Volume (ml)Mean Ablation ShapeSt Dev Ablation Shape176061.770.0822.480.1844.080.6360.710.0361721062.900.1792.920.40712.952.7700.900.0841751064.020.1944.030.25034.164.1200.950.0391760064.230.2424.150.35139.257.2000.960.0431790064.820.0754.780.23258.164.1200.970.01617120065.200.3745.050.32171.9911.9900.950.0522530063.650.2263.680.12225.874.6300.940.0352560064.670.1514.500.03751.394.0400.960.0253512063.050.1383.130.16315.281.4810.940.0443524063.780.1173.680.17227.611.9130.950.0333536064.280.1724.150.28140.004.9600.950.0363560065.030.2944.750.18763.258.5400.930.038 Open table in a new tab
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