Lasers for Medical Applications

Diagnostics, Therapy and Surgery

Helena Jelínková

• Éditeur: Woodhead Publishing
• Année: 2013
• ISBN:
  9780857097545
• Sujet: Tecnología e ingeniería
• Sous-sujet: Ciencias de los materiales

Lasers have a wide and growing range of applications in medicine. Lasers for Medical Applications summarises the wealth of recent research on the principles, technologies and application of lasers in diagnostics, therapy and surgery.Part one gives an overview of the use of lasers in medicine, key principles of lasers and radiation interactions with tissue. To understand the wide diversity and therefore the large possible choice of these devices for a specific diagnosis or treatment, the respective types of the laser (solid state, gas, dye, and semiconductor) are reviewed in part two. Part three describes diagnostic laser methods, for example optical coherence tomography, spectroscopy, optical biopsy, and time-resolved fluorescence polarization spectroscopy. Those methods help doctors to refine the scope of involvement of the particular body part or, for example, to specify the extent of a tumor. Part four concentrates on the therapeutic applications of laser radiation in particular branches of medicine, including ophthalmology, dermatology, cardiology, urology, gynecology, otorhinolaryngology (ORL), neurology, dentistry, orthopaedic surgery and cancer therapy, as well as laser coatings of implants. The final chapter includes the safety precautions with which the staff working with laser instruments must be familiar.With its distinguished editor and international team of contributors, this important book summarizes international achievements in the field of laser applications in medicine in the past 50 years. It provides a valuable contribution to laser medicine by outstanding experts in medicine and engineering.

• Describes the interaction of laser light with tissue
• Reviews every type of laser used in medicine: solid state, gas, dye and semiconductor
• Describes the use of lasers for diagnostics

1

Introduction: the history of lasers in medicine

H. Jelínková, Czech Technical University in Prague, Czech Republic

Abstract:

On the background of the history of laser medicine, the basic principles of the interaction of laser radiation with tissue are explained and the main factors influencing the results of the interaction are analyzed. After description of .laser radiation and tissue main characteristics, the primary factors of laser radiation interaction with tissue, including spectral reflection, refraction, absorption, scattering, and transmission, are defined. Secondary factors, i.e. photochemical or photothermal interaction (non-ablative heating, vaporization), photo-ablation, plasma-induced ablation, and photo-disruption are then mentioned.

Key words

laser medicine history

interaction of the laser radiation with tissue

1.1 Introduction

The application of the laser in medical treatment is based on the interaction of laser radiation with biological tissue. Laser radiation can be included in a large category of electromagnetic radiation generated by many types of radiation sources such as the sun, fire, bulbs, electric discharge, plasma, etc. From a historical point of view, the sun’s radiation has been used as a therapeutic tool for the treatment of various pathological phenomena or to improve health for many centuries. The ancient Egyptians are believed to have used ‘sunbathing’ as phototherapy, and the ancient Greeks and Romans used sunlight for phototherapy or heliotherapy (Bertolotti, 2005). Sun radiation also initiated the action of light-sensitive substances applied to the skin, leading to a particular tissue healing process. The Egyptians and Indians treated skin diseases such as vitiligo or leukoderma with the help of this method, which is today called photochemotherapy. The Chinese have historically used the sun in order to cure (or at least slow down) the progress of diseases such as rickets, skin cancer or even psychosis.

During the Middle Ages, the use of light for medical treatment was interrupted, possibly due to medieval morals prohibiting nudity in public. At the end of the nineteenth century, the Swiss healer Arnold Rikli reintroduced the medical profession to the positive effects of sunlight and used these effects as the basis of successful natural healing methods. Louis Kuhne and Heinrich Lahman also used heliotherapy for the care of some illnesses (Friedhelm and Wade, 1994). Significant work in phototherapy was done by Danish physician Niels Ryberg Finsen. His works ‘On the effects of light on the skin’ (1893), ‘The use of effects of light on the skin’ (1896), and ‘La Photothérapie’ (1899) were the basis on which Finsen was awarded the Nobel Prize¹ for his results in the treatment of patients with various cutaneous diseases.

Besides the knowledge of the positive medicinal effects of sun radiation, the negative impact of solar radiation on the human eye has also been known since the time of Plato and Socrates. A description of central vision loss from gazing at the sun was provided by Theophilus Bonetus in the seventeenth century. It was observed that solar radiation can damage the structure of the inner eye. The first experiments regarding retinal damage by sunlight were performed by Czerny in 1867. In the twentieth century, further experiments were performed by Maggiore (1927) and Moran-Salas (1940) (Palanker et al., 2011). The basic knowledge that light has the potential to damage the eye was slowly converted into a method of treating the eye structures. In 1949 G. Meyer-Schwickerath focused sunlight onto patients’ retinas to treat melanomas for the first time. Meyer-Schwickerath was also involved in the construction of the first eye photocoagulator, which used solar radiation to weld a detached part of the retina (1949); in the following years he developed treatments for retinal tears, macular holes, and diabetic retinopathy with the help of photocoagulation, and also solved other problems of the retina and macula using the Zeiss xenon arc light photocoagulator (Meyer-Schwickerath, 1989). A 1000 W arc lamp was used to direct light into the eye for 1 s intervals to form scars attaching the retina to the eyeball.

Red ruby laser radiation was generated for the first time by Theodore Maiman in May 1960 (Maiman, 1960) (see Chapter 2). Following this initial breakthrough, engineers and physicists began to test the possible applications of laser radiation. They found that it is possible to drill holes through razor blades using ruby laser radiation, suggesting that it might be suitable for other technological applications. Physicians also compared laser light with the other light sources that had been used in medical treatment up to this time. Because light radiation was already in widespread use for the treatment of diseases, mainly in dermatology and during the twentieth century also in ophthalmology (as was documented above, and see also Chapter 13), the first successful experiments using laser light for such treatments were carried out very soon after laser light was first generated.

The first real success in terms of laser technology was in the care of a detached retina. Arc-lamp radiation was replaced by millisecond red ruby laser pulses. After successfully treating rabbits for detached retina, the ophthalmologist Ch. J. Campbell and then Ch. Zweng² performed the first successful operations on a human patient (Koester and Campbell, 2003).

Ruby laser light interaction with the skin was also under investigation at this time. In 1961, Leon Goldman became the first researcher to use laser radiation to treat a human skin disease when he treated a skin melanoma. In 1963, Goldman and his co-workers published the first study on the effects of laser radiation on the skin, describing the selective destruction of skin pigmented structures (including hair follicles) using a ruby laser beam. They noted highly selective injury of pigmented structures (black hair) with no evident change in the white skin underneath (Goldman et al., 1963). This method later became popular for removing birthmarks, nevi and tattoos with minimal scarring. In 1966, Goldman supervised the first operation in which laser radiation was used to remove a tumor without causing bleeding. The laser’s pulses of light cut skin and cauterized blood vessels simultaneously, paving the way for several other applications (Goldmann, 1967; Waynant, 2002; Geiges, 2011). The difficulty lay in controlling the power output and the delivery rate of the laser radiation, as well as the relatively poor absorptive capacity of some types of tissue for ruby laser light. With the development of laser physics and successive discoveries of other aspects of laser technology³ such as the generation of new wavelengths, radiation with various energy levels, high power and small beam divergence, a new branch of science dealing with the applications of ‘laser medicine’ began to develop.

Other laser treatments in medicine followed almost in parallel with the news in laser science. Soon after the discovery of the Nd:glass laser, its near-infrared (IR) radiation was first used for medical treatment. For people with diabetes, a significant development occurred in 1968 when F. L’Esperance, E. Gordon, and E. Labuda successfully used an argon ion laser for the treatment of diabetic retinopathy (L’Esperance, 1969; L’Esperance and James, 1981). This laser has further potential applications in treating port-wine stain marks. Studies were also carried out on the possible treatment of vascular malformations using argon laser technology. The discovery of CO₂ and Nd:YAG lasers in 1964 was also of great importance for medicine. These two lasers work in the near-IR (Nd:YAG) and far-IR (CO₂) regions of the spectrum, and have been the most common laser devices in medical practice up to the present time. It was found that a Nd:YAG and CO₂ laser beam could cut tissue like a scalpel, but with minimal blood loss. Using an out-of-focus beam created the potential for a larger spot size, making hemostasis possible. This made Nd:YAG and CO₂ lasers a helpful tool in surgery on vasculated organs such as liver, oral mucosa and gynecological tissue. The surgical uses of CO₂ lasers were investigated extensively from 1967 to 1970 by pioneers such as T. Polanyi and G. Jako, and the use of the CO₂ laser in otolaryngology and gynecological surgery became well established in the early 1970s. Advances in this field were also made by V. C. Wright and I. Kaplan, who developed the application of CO₂ lasers to general surgery (Wright, 1982; Kaplan, 1984).

Together with the discovery of new laser types, the development of new ways of using lasers influenced the discovery of new medical treatments. In 1962 Hellwarth and McClung discovered the potential for generating short, tens of nanoseconds (10^–9 s) long, pulses, which provided a much higher power laser than those previously available. These pulses were therefore named ‘giant’ pulses (Hellwarth and McClung, 1962) (for an explanation of this phenomenon, see Chapter 5). Using such giant pulses, the most striking results have been obtained with the removal of tattoos and nevi. In 1964 Maher described the generation of the first spark produced by intense laser radiation. Laser pulses incorporating both high power levels and sparks ...

Table des matières

• Cover image
• Title page
• Table of Contents
• Copyright
• Contributor contact details
• Woodhead Publishing Series in Electronic and Optical Materials
• Preface
• Chapter 1: Introduction: the history of lasers in medicine
• Part I: Laser–tissue interaction
• Part II: Types of laser used in medicine
• Part III: Lasers in diagnostics
• Part IV: Laser therapy and surgery
• Index