Size Selective Characterization and Particle Emission Rates during a Simulated Medical Laser Procedure

Introduction Investigations on medical laser interaction with tissue have suggested laser operational parameter settings influence LGAC emission, but this has not been systematically explored. Characterization of medical LCAG particles may improve exposure control strategies and provide insight on the ability of particles to transport viable cellular material. Methods A laboratory-based simulated surgical procedure was designed to characterize LGAC and to estimate exposures in theoretical hospital settings. Two medical lasers (CO2, l =10,600 nm and Ho:YAG, l =2100 nm) were used, varying three operational parameters (beam diameter, PRF, and power) between two levels and the resultant plume was collected using two real-time size selective particle counters and polycarbonate filters in an emission chamber. ANOVA was used to determine the influence of operational parameter settings on size-specific particle emission rate, and particles collected on polycarbonate filters were imaged using a SEM to study particle characteristics. Emission rates were applied to a two-zone exposure model to estimate PM concentrations in ORs. Results Beam diameter was the most influential parameter for both lasers followed by power. An increase in power and decrease in beam diameter led to increased particle emissions for the Ho:YAG laser. For the CO2 laser, higher power led to decreased emission rates of small particles and an increase for large particles while a smaller beam diameter led to an increase of particle emissions for some size ranges (0.02 to 1 µm and 3 to 10 µm) and a decrease in others (0.3 to 0.5 µm and 1 to 3 µm). Particle size observed under an SEM varied between 1 and 10 mm for the Ho:YAG laser and between 1 and 50 mm for the CO2 laser. Visible particle shapes included fibers, foam, and conglomerate particles. Modeled concentrations for the near-field ranged between 0.03 to 0.5 mg/m3 and between 0.01 to 0.4 mg/m3 in the far-field. Discussion/Conclusion The methods used in this study provide a foundation for future investigations to better estimate particle-size dependent emission rates for additional laser operational parameters in order to inform occupational exposure control strategies.