Microwave ablation of the liver abutting the stomach: Insulating effect of a chitosan-based thermosensitive hydrogel

Abstract

Purpose: Collateral thermal injury can occur as a serious complication of microwave ablation. This study aimed to assess the insulating effect of a thermosensitive, chitosan-based hydrogel during the percutaneous microwave ablation of liver tissue abutting the stomach. Materials and methods: Thermometry needles (R1–R4) were positioned at 5-mm intervals from a thermal source to measure in vitro the temperature differences due to the hydrogel (R1 closest to the thermal source). Subsequently, two groups of eight rabbits each were injected with 10 mL of hydrogel solution or 410 ± 95 mL of 5% saline between the liver and stomach wall. A control group of eight rabbits received no ablation protection measures. The livers were ablated with 40 W for 300 s in 24 ablation zones. The severity of thermal injury to the stomach wall was assessed histologically. Results: In vitro, the mean maximum temperature difference between the R1 and R2 thermometry needles was 31.3° ± 0.1 °C. When R1 was over 60 °C, the mean temperatures at R2, R3, and R4 were 29.8° ± 0.1 °C, 18.6 ± 0.3 °C, and 18.1° ± 0.1 °C, respectively. After ablation for 300 s, the maximum temperature at R2 was 48.7° ± 0.2 °C. None of the rabbits injected with gel showed any injury after ablation; however, the other two groups showed varying degrees of thermal injury. Conclusion: The in situ gel protected the adjacent stomach wall from injury during percutaneous microwave ablation of liver tissue. Although the present technique appears promising, further studies are necessary prior to clinical application.

• Chitosan
• injury
• liver neoplasms
• microwave ablation
• thermosensitivity