Radiometric surface temperature measurements during dye-assisted laser skin closure: In vitro and in vivo results

Background and Objective: A thermal camera was used to measure surface temperatures during laser skin welding to provide feedback for optimization of the laser parameters. Study Design/Materials and Methods: Two-centimeter- long, full-thickness incisions were made in guinea pig skin in vitro and in vivo. India ink was applied to the incision edges, which were then mechanically apposed. Continuous-wave, 1.06-μm Nd:YAG laser radiation was scanned over the incisions, producing an effective pulse duration of ~100 msec. Cooling durations between scans of 1.6, 4.0, and 8.0 sec were studied in vitro. A 5-mm-diameter laser spot was used with the power kept constant at 10 W. Thermal images were obtained at 30 frames per second with a thermal camera detecting 3-5 μm radiation. Surface temperatures were recorded at 0, 1, and 6 mm from the center line of the incision. Results/Conclusions: Cooling durations of 1.6 and 4.0 seconds in vitro resulted in temperatures at the weld site that remained above ~65°C for prolonged periods of time. Cooling durations of 8.0 seconds were sufficient both in vitro and in vivo to prevent a significant rise in baseline temperatures at the weld site over time.