Medical Lasers and Their Safe Use

This text was designed for the physicians, nurses, technical personnel, and staff members of medical facilities using lasers for surgical, therapeutic, and diagnostic purposes. The objective is to provide an understanding of the potential health and safety hazards associated with the use of medical laser systems and the precautions needed to use them safely. To do this, it is necessary to have an awareness of applicable standargs and regula­ tions that apply to laser use. This book is not intended as a substitute for the American National Standards Institute (ANSI) Z-136. 3, "Safe Use of Lasers in Health Care Facilities," but to facilitate its implementation as well as the implementation of the many other related regulations and guidelines that are pertinent. These other regulations include the Medical Device Amendments to the Food and Drug Act, the Federal Laser Product Performance Standards issued under the Radiation Control for Health and Safety Act, and applicable regulations of the Occupational Safety and Health Administration (OSHA). The text is organized to provide first an overview of laser hazards, laser surgical applications, and laser biological effects. General safety control measures and safety standards are then presented. Because laser tech­ nology is rapidly evolving, these general guidelines will allow safe use of new laser systems as they become available. Finally, specific safety guide­ lines and precautions are provided for specialized laser applications in the different health care specialties.

1. Introduction to Medical Laser Systems.- Light and Electromagnetic Radiation.- Generation of Laser Light.- Lasers and How They Work.- Energy Source.- Laser Action.- The Resonant Cavity.- Properties of Laser Light.- Monochromaticity.- Directionality.- Coherence.- Brightness.- Wavelength.- Pulsed and Continuous-Wave Lasers.- Q-Switching.- Mode Locking.- Beam Profiles.- Delivery Systems.- Laser System Control.- 2. Laser Systems.- Categories of Lasers.- Solid-State Lasers.- Gas Lasers.- Dye Lasers.- Semiconductor Diode Lasers.- Metal Vapor Lasers.- Free-Electron Lasers.- Specific Lasers Used in Medical Practice.- The Ruby Laser.- The Nd.YAG Laser and Related Solid-State Lasers.- The Co2 Gas Lasers.- The Excimer Laser and Other Ultraviolet Sources.- The Dye Laser: Pulsed and CW.- The Diode Laser.- 3. Laser-Tissue Interactions.- The Eye.- The Skin.- Other Tissues.- Terminology.- Spectral Band Designations.- Energy and Power.- Irradiance and Radiant Exposure.- Fluence.- Thermal Diffusion.- Fibers and Contact Tips.- Categories of Laser-Tissue Interaction.- Photocoagulation.- Photothermal Ablation (Vaporization).- Photochemical Ablation.- Photodisruption.- Photochemical Interactions.- 4. Laser Applications in Medical Practice.- General Surgery.- Tissue Interactions: Incision, Ablation, Coagulation.- Endoscopic Laser Surgery.- Dermatology.- Surface Vascular Lesions.- Pigment and Tattoo Removal.- Epithelial Lesions.- Ophthalmology.- Ophthalmic Photocoagulators.- Photodisruptors.- Ophthalmic Diagnostic Lasers.- Laser Corneal Surgery.- Cardiovascular and Chest Surgery.- Tissue Welding and Vessel Anastomosis.- Laser Angioplasty and Endarterectomy.- Gynecologic Lasers.- Otolaryngology and Head and Neck Surgery.- Neurosurgery.- Tumor Surgery.- Excision and Ablation.- Photodynamic Therapy.- Urology.- Anesthetic Considerations.- Biostimulation or “Soft” Lasers.- Diagnostic Lasers.- 5. Laser Injury and Potential Hazards.- Hazards to the Eye.- The Retina.- The Cornea and Lens.- Ocular Hazards of Specific Wavelength.- Skin Hazards.- Personnel Susceptibility.- Patient.- Fire Hazards.- Surgeons.- Surgical Assistants.- Bystanders.- Service Personnel.- 6. Safety Standards and Laser Exposure Limits.- National and International Standards.- ANSI Standards.- Federal Laser Performance Standard.- International Standards and Guidelines.- Laser Safety Exposure Limits.- Determining an EL.- Exceeding the EL.- Laser Hazard Classification.- Class 1 Laser Products.- Class 2 Laser Products.- Class 3 Laser Products.- Class 4 Laser Products.- Laser Hazard Assessment.- 7. Ancillary Hazards of Laser Use.- Electrical Hazards.- Airborne Contaminants (Vaporized Target Tissue).- Pathogens.- Chemical Contaminants―Fumes, Aerosols, and Vapors.- Protective Measures.- Chemical Hazards.- Nonlaser Light Sources.- Mechanical Hazards.- 8. Investigational and Research Lasers.- Introduction: Investigational and Prototype Lasers.- Investigational Lasers and the FDA.- Medical Device Regulations.- The Institutional Review Board.- The 1990 Amendments to the Medical Device Act.- Use of Approved Lasers in a Nonapproved Manner.- Laser Safety in the Experimental Environment.- Equipment Safety: Ancillary Hazards.- Laser Eye Protection.- Laser Accident History.- Hazard Evaluation Report for New Laser Systems.- 9. Engineering Control Measures.- Concepts of Engineering Controls.- Laser System Design and Required System Safety Features.- The Protective Housing.- Prevention of Access.- The Beam Delivery System.- Operation, Maintenance, and Service.- Beam Delivery Disconnect.- Key-Switch Master Control.- Remote Interlock (Control) Connector.- Viewing Optics.- Requirements.- Invisible Beam Filtration.- Color Rendering.- Ophthalmic Flashbacks.- Auxiliary Optics.- Beam Attenuator.- Power Meters.- Beam Emission Indicator.- Guarded Switch.- Labeling.- Ancillary Hazards.- The Nominal Hazard Zone and Focused Beams.- Laser Room Design and Controlled Areas.- Doorway Interlocks.- Warning Signs and Lights.- Light Leaks―How Important?.- Controlling Reflections.- Table, Cabinet, and Instrument Surfaces.- Cabinets and Wall Surfaces in the Laser Surgical Suite.- Software and Electronic Failures.- 10. Personnel Protective Equipment.- Eye Protection.- Specifying Laser Eye Protectors.- Optical Density.- Visual Transmittance.- Filter Damage.- Comfort and Fit.- Filter Testing.- White Light Protection.- Methods of Construction.- Skin Protection.- Respiratory Protection.- Available Respirators.- 11. Administrative Control Measures.- Laser Safety Program.- Laser Safety Committee.- Laser Safety Officer.- Laser Safety Training.- Laser Credentialing.- Background.- Inpatient or Hospital-Based Surgery.- Outpatient or Office-Based Surgery.- Examples of Standard Practice.- Sample Laser Safety Standing Operating Procedures.- Hospital Laser Safety Regulations.- Scope of a Regulation.- Example of Regulations.- FDA Administrative Controls.- Appendix 1.- Appendix 2.- Appendix 3.- Appendix 4.- Appendix 5.- Appendix 6.- Appendix 7.- Appendix 8.- Appendix 9.- Appendix 10.- Appendix 11.- 12. Medical Surveillance.- History.- Current Aims of Medical Surveillance of Laser Workers.- Population to be Monitored.- Problems.- Definition of Population.- Frequency.- Medical Examinations.- Medical History.- Vision Testing.- Aims.- Ophthalmic Examination.- Ocular History.- Vision Screening Examinations.- Ophthalmologic Examination Following an Incident.- Coincidental Pathology and Malingering.- Lesions that Mimic Laser Injuries.- Laser-Specific Testing.- 13. Laser Checkout and Demonstration Procedures.- Simple Tests of Laser Operation.- Philosophy of Check Tests.- The 1-Joule Test for the CO2 Laser.- Optical Viewing System Alignment for CO2 Lasers.- Safety Filters in Viewing Optics.- Nd:YAG Ophthalmic Photodisruptor Tests.- Aiming Beam Alignment.- Optical Breakdown in Air.- Target Box.- Ablative Lasers.- Safeguards During Demonstrations and Training.- Installation of Lasers at Medical Equipment Exhibitions and Training Sites.- Appendices: Useful Reference Information.- Appendix 1: Abbreviations.- Appendix 2: Simplified Glossary.- Appendix 3: Occupational Safety Limits.- Appendix 4: Regulatory and Standardization Bodies.- Appendix 5: Laser Safety Equipment.- Appendix 6: Variances.