Comparison of pulsed CO2 laser ablation at 10.6 μm and 9.5 μm

Abstract

Background and Objective: The pulsed CO2 laser has received attention because of its successful application to dermatologic surgery and burn debridement surgery. Despite impressive results, tissue removal using pulsed CO2 laser irradiation has not been optimized. We examined the ablation processes by performing mass removal and thermal injury experiments at wavelengths where tissue water is the primary absorber (10.6 μm), and where water and collagen have comparable absorption (9.5 μm). Study Design/Materials and Methods: Samples of porcine reticular dermis were irradiated with 180-ns laser pulses at either wavelength. Tissue removal was measured using a digital balance. Thermal injury was assessed using a microscope with a calibrated reticle after hematoxylin and eosin staining. Results: Tissue removal using 10.6-μm radiation resulted in a heat of ablation of 3,740 J/g, an ablation threshold of 1.15 J/cm2, and a zone of thermal injury of 53 μm. By contrast, tissue removal using 9.5-μm radiation resulted in a heat of ablation of 3,330 J/g, an ablation threshold of 1.47 J/cm2, and a zone of thermal injury of 34 μm. The differences in ablation threshold and thermal injury were statistically significant. Conclusion: Pulsed CO2 laser irradiation at 9.5 μm removes tissue more efficiently and with a smaller zone of thermal injury than at 10.6 μm.