Medical Lasers and Their Safe Use

Transcription

1 Medical Lasers and Their Safe Use

2 David H. Sliney Stephen L. Trokel Medical Lasers and Their Safe Use With 88 Illustrations Springer-Verlag New York Berlin Heidelberg London Paris Tokyo Hong Kong Barcelona Budapest

3 David H. Sliney, Ph.D. Consulting Physicist Fallston, MD 21047, USA Stephen L. Trokel, M.D. Professor of Clinical Opthalmology Columbia-Presbyterian Medical Center Harkness Eye Institute New York, NY 10032, USA Library of Congress Cataloging-in-Publication Data Sliney, David H. Medical lasers and their safe useldavid H. Sliney, Stephen L. Trokel. p. cm. Includes bibliographical references and index. ISBN-13: DOl: / e-isbn-13: Lasers in medicine-safety measures. I. Trokel, Stephen L. II. Title. [DNLM: 1. Laser Surgery-adverse effects. 2. Laser Surgerystandards. 3. Lasers-adverse effects. 4. Lasers-standards. 5. Safety. WB 117 S633m] R857.L37S '.28-dc20 DNLMIDLC for Library of Congress Printed on acid-free paper Springer-Verlag New York Inc. Softcover reprint of the hardcover 1 st edition 1993 All rights reserved. This work may not be translated or copied in whole or in part without the written permission of the publisher (Springer-Verlag New York, Inc., 175 Fifth Avenue, New York, NY 10010, USA), except for brief excerpts in connection with reviews or scholarly analysis. Use in connection with any form of information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed is forbidden. The use of general descriptive names, trade names, trademarks, etc., in this publication, even if the former are not especially identified, is not to be taken as a sign that such names, as understood by the Trade Marks and Merchandise Marks Act, may accordingly be used freely by anyone. While the advice and information in this book is believed to be true and accurate at the date of going to press, neither the authors nor the editors nor the publisher can accept any legal responsibility for any errors or omissions that may be made. The publisher makes no warranty, express or implied, with respect to the material contained herein. Production managed by Christin R. Ciresi; manufacturing supervised by Jacqui Ashri. Typeset by Best-set Typesetter Ltd., Hong Kong

4 Preface 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 regulations 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 technology is rapidly evolving, these general guidelines will allow safe use of new laser systems as they become available. Finally, specific safety guidelines and precautions are provided for specialized laser applications in the different health care specialties. Because laser safety is a multidisciplinary subject, it has not been possible to consistently maintain rigorous scientific terminology within this text. We have tried to simplify description of complex physical concepts and biological phenomena so that they may be appreciated by the widest audience. v

5 Contents Preface v 1. Introduction to Medical Laser Systems 1 Light and Electromagnetic Radiation 1 Generation of Laser Light 6 Lasers and How They Work 7 Energy Source 8 Laser Action 9 The Resonant Cavity 10 Properties Of Laser Light 11 Monochromaticity 11 Directionality 11 Coherence 11 Brightness 12 Wavelength 13 Pulsed and Continuous-Wave Lasers 13 Q-Switching 15 Mode Locking 17 Beam Profiles 18 Delivery Systems 19 Laser System Control Laser Systems 23 Introduction 23 ~~~~~~ n Solid-State Lasers 25 Gas Lasers 25 Dye Lasers 28 Semiconductor Diode Lasers 29 Metal Vapor Lasers 30 Free-Electron Lasers 30 Specific Lasers Used in Medical Practice 30 The Ruby Laser 30 The Nd: Y AG Laser and Related Solid-State Lasers 30 vii

6 viii Contents The CO 2 Gas Lasers 32 The Excimer Laser and Other Ultraviolet Sources 32 The Dye Laser: Pulsed and CW 32 The Diode Laser Laser-Tissue Interactions 35 Introduction 35 The Eye 35 The Skin 37 Other Tissues 37 Terminology 38 Spectral Band Designations 38 Energy and Power 39 Irradiance and Radiant Exposure 40 Fluence 40 Thermal Diffusion 42 Fibers and Contact Tips 42 Categories of Laser-Tissue Interaction 42 Photocoagulation 42 Photothermal Ablation (Vaporization) 44 Photochemical Ablation 45 Photo disruption 45 Photochemical Interactions Laser Applications in Medical Practice 51 General Surgery 51 Tissue Interactions: Incision, Ablation, Coagulation 51 Endoscopic Laser Surgery 52 Dermatology 54 Surface Vascular Lesions 54 Pigment and Tattoo Removal 55 Epithelial Lesions 55 Ophthalmology 55 Ophthalmic Photocoagulators 55 Photodisruptors 59 Ophthalmic Diagnostic Lasers 60 Laser Corneal Surgery 61 Cardiovascular and Chest Surgery 62 Tissue Welding and Vessel Anastomosis 62 Laser Angioplasty and Endarterectomy 63 Gynecologic Lasers 63 Otolaryngology and Head and Neck Surgery 63 Neurosurgery 65 Tumor Surgery 67 Excision and Ablation 67

7 Contents ix Photodynamic Therapy 67 Urology 68 Anesthetic Considerations 68 Biostimulation or "Soft" Lasers 68 Diagnostic Lasers Laser Injury and Potential Hazards 72 Introduction 72 Hazards to the Eye 72 The Retina 72 The Cornea and Lens 75 Ocular Hazards of Specific Wavelength 76 Skin Hazards 77 Personnel Susceptibility 79 Patient 79 Fire Hazards 80 Surgeons 81 Surgical Assistants 81 Bystanders 82 Service Personnel Safety Standards and Laser Exposure Limits 87 Introduction 87 National and International Standards 87 ANSI Standards 87 Federal Laser Performance Standard 88 International Standards and Guidelines 88 Laser Safety Exposure Limits 89 Determining an EL 90 Exceeding the EL 91 Laser Hazard Classification 91 Class 1 Laser Products 92 Class 2 Laser Products 94 Class 3 Laser Products 94 Class 4 Laser Products 95 Laser Hazard Assessment Ancillary Hazards of Laser Use 98 Introduction 98 Electrical Hazards 98 Airborne Contaminants (Vaporized Target Tissue) 102 Pathogens 102 Chemical Contaminants-Fumes, Aerosols, and Vapors 103 Protective Measures 104 Chemical Hazards 104

8 x Contents Nonlaser Light Sources 108 Mechanical Hazards Investigational and Research Lasers 113 Introduction: Investigational and Prototype Lasers 113 Investigational Lasers and the FDA 113 Medical Device Regulations 114 The Institutional Review Board 115 The 1990 Amendments to the Medical Device Act 116 Use of Approved Lasers in a Nonapproved Manner 117 Laser Safety in the Experimental Environment 118 Equipment Safety: Ancillary Hazards 120 Laser Eye Protection 120 Laser Accident History 121 Hazard Evaluation Report for New Laser Systems 122 Appendix Engineering Control Measures 127 Concepts of Engineering Controls 127 Laser System Design and Required System Safety Features 127 The Protective Housing 129 Prevention of Access 129 The Beam Delivery System 130 Operation, Maintenance, and Service 130 Beam Delivery Disconnect 132 Key-Switch Master Control 132 Remote Interlock (Control) Connector 133 Viewing Optics 134 Requirements 134 Invisible Beam Filtration 134 Color Ren<;lering 135 Ophthalmic Flashbacks 135 Auxiliary Optics 136 Beam Attenuator 137 Power Meters 137 Beam Emission Indicator 140 Guarded Switch 141 Labeling 142 Ancillary Hazards 144 The Nominal Hazard Zone and Focused Beams 144 Laser Room Design and Controlled Areas 146 Doorway Interlocks 147 Warning Signs and Lights 147 Light Leaks-How Important? 147 Controlling Reflections 148 Table, Cabinet, and Instrument Surfaces 148

9 Contents XI Cabinets and Wall Surfaces in the Laser Surgical Suite 151 Software and Electronic Failures Personnel Protective Equipment 153 Eye Protection 153 Introduction 153 Specifying Laser Eye Protectors 154 Optical Density 156 Visual Transmittance 156 Filter Damage 158 Comfort and Fit 160 Filter Testing 160 White Light Protection 161 Methods of Construction 161 Skin Protection 162 Introduction 162 Respiratory Protection 164 Introduction 164 Available Respirators Administrative Control Measures 167 Laser Safety Program 167 Laser Safety Committee 168 Laser Safety Officer 169 Laser Safety Training 170 Laser Credentialing 171 Background 171 Inpatient or Hospital-Based Surgery 172 Outpatient or Office-Based Surgery 174 Examples of Standard Practice 175 Sample Laser Safety Standing Operating Procedures 175 Hospital Laser Safety Regulations 176 Scope of a Regulation 176 Example of Regulations 176 FDA Administrative Controls 177 Appendix Appendix Appendix Appendix Appendix Appendix Appendix Appendix Appendix Appendix Appendix

10 XII Contents 12. Medical Surveillance 190 Introduction 190 History 191 Current Aims of Medical Surveillance of Laser Workers 191 Population to be Monitored 192 Problems 192 Definition of Population 192 Frequency 192 Medical Examinations 193 Medical History 193 Vision Testing 193 Aims 193 Ophthalmic Examination 194 Ocular History 195 Vision Screening Examinations 196 Ophthalmologic Examination Following an Incident 196 Coincidental Pathology and Malingering 197 Lesions that Mimic Laser Injuries 202 Laser-Specific Testing Laser Checkout and Demonstration Procedures 204 Simple Tests of Laser Operation 204 Philosophy of Check Tests 204 The I-Joule Test for the CO 2 Laser 205 Optical Viewing System Alignment for CO 2 Lasers 205 Safety Filters in Viewing Optics 206 Nd:YAG Ophthalmic Photodisruptor Tests 207 Aiming Beam Alignment 207 Optical Breakdown in Air 207 Target Box 207 Ablative Lasers 208 Safeguards During Demonstrations and Training 208 Installation of Lasers at Medical Equipment Exhibitions and Training Sites 210 Appendices: Useful Reference Information 211 Appendix 1: Abbreviations 211 Appendix 2: Simplified Glossary 213 Appendix 3: Occupational Safety Limits 216 Appendix 4: Regulatory and Standardization Bodies 220 Appendix 5: Laser Safety Equipment 221 Appendix 6: Variances 223 Index 225