Comparison between Continuous and Intermittent Ablation Using a 1470-nm Radial 2ring Slim Fiber Laser: Safety Implications for Percutaneous Ablation of Perforators

Abstract

Objectives: Ablation is a treatment modality involving the destruction of diseased tissue through direct contact or direct energy absorption. This comparative experimental study aimed to understand the differences between 2 types of ablation, continuous and intermittent ablation. Methods: Using albumen and agar as media, we compared medium denaturation and temperature, respectively, between the continuous wave (continuous ablation) and pulse (intermittent ablation) modes using a 1470-nm Radial 2ring slim fiber laser (output=6.5 W). Experiment 1: We measured the amount of denatured albumen following ablation by comparing the continuous wave mode with three types of pulse wave modes with duration and pause rations of 1 : 1 s, 1 : 2 s, and 1 : 3 s. We then calculated the mean area of denatured albumen using photographs. Experiment 2: We assessed the temperature with a thermistor probe positioned 0 mm and 3 mm from the catheter prism in the ager medium. We measured the mean maximum temperature, mean temperatures at 65.0 J and 130.0 J, and the mean time to reach at 40, 50, 60, 70, and 80°C. Results: Experiment 1: There were greater changes in the albumen around the fiber prism center than that at the fiber prism tip. Longer pause periods led to less degenerative changes in the albumen. Experiment 2: The temperature increased rapidly in the continuous wave mode both at 0 mm and 3 mm. In contrast, in the pulse wave mode, temperature increased slowly and in a ‘sawtooth’ wave pattern. The mean maximum temperature in the continuous wave mode was 108.0±13.4°C and 98.0±3.1°C at 0 and 3 mm, respectively, while the corresponding values in the pulse mode were 95.5±8.4°C and 71.6±2.8°C. Temperatures at 65.0 J were 98.8±3.1 and 91.4±8.1°C at 0 and 3 mm in the continuous wave mode and 76.8±11.2 and 48.4±9.5°C in the pulse wave mode, while the corresponding values at 130.0 J were 88.7±2.6 and 91.5±6.5°C for the continuous wave mode and 76.1±13.2 and 69.3±13.0°C for the pulse wave mode. Conclusion: Intermittent ablation increases temperature slowly, is more effective on distant sites, and may cause less tissue damage depending on the duration: pause ratio. Continuous ablation causes a rapid increase in temperature and may be more effective for targeted ablation. Our findings suggest that there was less heat diffusion into the surrounding tissue when using intermittent ablation than when using continuous ablation.