Basic principles of medical lasers
- Henri G Colt, MD
Henri G Colt, MD
- Professor of Medicine
- University of California Irvine
Lasers are devices that emit a single, coherent wavelength of electromagnetic radiation that is used to cut, coagulate, or ablate tissue for a variety of clinical applications. Laser systems produce a variety of wavelengths of varying pulse duration and energy levels. Computer-based imaging and guidance systems allow procedures to be performed precisely, quickly, and with greater control. Although lasers are commonly used superficially for cutaneous and ocular applications, smaller, efficient laser delivery systems are available for minimally invasive applications, including endoscopy, bronchoscopy, laparoscopy, and endovenous ablation.
The safe and appropriate use of lasers requires a trained clinician with a working knowledge of laser delivery systems and laser-tissue interactions to achieve the desired clinical effect while minimizing complications.
The basic principles of medical lasers will be reviewed here. The use and effectiveness of lasers for specific clinical indications are discussed in separate topic reviews. (See 'Clinical utility of lasers' below.)
Light is electromagnetic radiation within the range of wavelength that is visible to the human eye. Medical lasers produce photons of electromagnetic energy that can be within, above, or below this range (figure 1). The ranges of wavelength for each region of the electromagnetic spectrum are as follows:
●Gamma rays: <0.1 nmTo continue reading this article, you must log in with your personal, hospital, or group practice subscription. For more information on subscription options, click below on the option that best describes you:
- Einstein, A. On the quantum theory of radiation. Physikal Zeitschr 1917; 18:121.
- Patel CKN, McFarlane RA, Faust WL . Selective excitation through vibrational energy and optical maser action in N2-CO2. Phys Rev 1964; 13:617.
- Boulnois, JL. Photophysical processes in recent medical laser developments: A review. Lasers Med Science 1986; 1:47.
- Nelson JS, Berns MW. Basic laser physics and tissue interactions. Contemporary Dermatology 1988; 2:1.
- Anderson RR, Parrish JA. Selective photothermolysis: precise microsurgery by selective absorption of pulsed radiation. Science 1983; 220:524.
- Kunishige JH, Goldberg LH, Friedman PM. Laser therapy for leg veins. Clin Dermatol 2007; 25:454.
- Wollina U, Schmidt WD, Hercogova J, Fassler D. Laser therapy of spider leg veins. J Cosmet Dermatol 2003; 2:166.
- Domínguez A, García JA, Costela A, Gómez C. Influence of the light source and bleaching gel on the efficacy of the tooth whitening process. Photomed Laser Surg 2011; 29:53.
- Polanyi TG. Physics of surgery with lasers. Clin Chest Med 1985; 6:179.
- Fisher JC. The power density of a surgical laser beam: its meaning and measurement. Lasers Surg Med 1983; 2:301.
- Goetz M, Kiesslich R, Dienes HP, et al. In vivo confocal laser endomicroscopy of the human liver: a novel method for assessing liver microarchitecture in real time. Endoscopy 2008; 40:554.
- Kiesslich R, Burg J, Vieth M, et al. Confocal laser endoscopy for diagnosing intraepithelial neoplasias and colorectal cancer in vivo. Gastroenterology 2004; 127:706.
- Wiesner C, Jäger W, Salzer A, et al. Confocal laser endomicroscopy for the diagnosis of urothelial bladder neoplasia: a technology of the future? BJU Int 2011; 107:399.
- Wu K, Liu JJ, Adams W, et al. Dynamic real-time microscopy of the urinary tract using confocal laser endomicroscopy. Urology 2011; 78:225.
- International Commission on Non-Ionizing Radiation Protection. ICNIRP statement--Protection of workers against ultraviolet radiation. Health Phys 2010; 99:66.
- http://www.icnirp.org (Accessed on January 19, 2011).
- http://fsmb.org/pdf/GRPOL_Laser_Regulation.pdf (Accessed on September 12, 2011).
- Occupational Safety and Health Administration. www.osha.gov (Accessed on March 31, 2009).
- http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_id=1705&p_table=DIRECTIVES (Accessed on February 09, 2011).
- ELECTROMAGNETIC SPECTRUM
- LASER PRINCIPLES
- Energy source
- Resonant chamber
- Active medium
- - Gas
- - Solid state
- - Semiconductor
- - Dye
- Laser beam production
- - Modes of operation
- LASER DELIVERY
- Tissue ablation
- - Laser parameters
- Tissue imaging
- CLINICAL UTILITY OF LASERS
- LASER SAFETY
- SUMMARY AND RECOMMENDATIONS