Laser Applications In Medicine And Biology

The use oflasers has entered almost every facet of medicine and biology. Therefore, it is to be expected that the reviews contained in this vol urne will reflect this diversity. As dinical acceptance has grown with various diagnostic and therapeutic applications, so has the need for a more thorough understanding of the theoretical background for each. This is especially true where a correlation is to be made between the theoretical background and the experimental data. It is only in this way that we can attain the optimal form of any therapy. The basic coupling ofenergy into biological tissue and its conversion into heat is characterized by many parameters. One ofthe most important is pulse duration. The review by Bimgruber in Chapter 6 shows how our knowledge ofthis parameter has been extended.The need for a more basic understanding of the interaction of electromagnetic energy with various kinds of materials has led to investigations on the nature of plasmas their stability and instability,and how theyexist. Docchio reviews the factors that cause them to occur at a specific locale and then to move away from that site. The availabilityofmany types ofoptical fibers has extended our ability to deliver laser energy from various types oflasers into almost anyselected location. This is particularly useful in medicine, where less invasive ap proaches to surgery and diagnosis are always helpful. However, as Rol and his colleagues explain, the power-handling capabilities ofoptical fibers limit many applications, particularly for short-duration, high-peak-power laser pulses.

In the intervening years since the publication of Volume I, the develop ment of new uses for the various types of lasers has proceeded at a rate more rapid than even the most fanciful dreamers envisioned. Of course, the main effort has been on the laser itself-new wavelengths, shorter and longer time domains for pulses, increases in power, and, most important, greater reliability. In its first stage the laser was described as a solution in search of a problem. The production of holograms was one problem whose solution seemed to involve large number of lasers. However that proposal had its own difficulties, for the hologram itself was described as a solution searching for a problem. But all of that now is a chapter from ancient history . On the current scene the laser is used in industrial pro duction lines, as a classroom item at all levels of education, and in com mercial usage such that the public is generally exposed to the laser devices themselves. Trial runs have been made, e. g. , of laser-based supermarket checkout devices and as commercial exploitation of this item begins, cer tainly many more similar adaptations will follow. However, the shift in emphasis from research usage of lasers to de velopment and production has been relative rather than absolute. The use of the laser in research has not lessened; rather it has grown at as fast a pace. Yet a similar trend is seen there also.

If a basic advance in physics has any practical applications, among the first are those in biology and medicine. This is quite striking when one considers even such unlikely things as the Mössbauer effect and X rays. Within a very short period of their discovery, they had welI-formulated biological and medical applications. The discovery of the laser is no exception. AIthough the theoretical basis for it was established in 1917 by Einstein, the techniques and materials necessary for building a laser were not then available. The laser has revitalized everything connected with optics. It has furnished the experimenter and the teacher with a pseudo-point source. It has translated many a theoretical experiment into one that can be realized practicalIy. The highly monochromatic and coherent aspects of the light, in addition to the high power levels that can be attained, add greatly to the usefulness in this regard. The industrial applictions range from punching holes in baby bottle nipples to a surveyor's instrument of such accuracy that it can plot tlie position of the moon relative to the earth within a few feet. Many years of very informal meeting on the subject of lasers in medicine and biology have been sponsored by the Gordon Research Conferences. The present book is an outgrowth of the discussions that took place at these meetings, aIthough it is in no sense a symposium report.

Much of the material in this book represents a departure from that presented earlier in the series. Volumes 1 and 2 presented almost exclusively reviews by American authors of American work. As science is international, it is rare that in two different parts of the world large groups of researchers in the same field remain relatively uninformed about each other's work. However, during the time since the initiation of this series, a large body of research has grown up in Russia that is almost unknown outside, as the original reports are largely untranslated. For this reason, an extensive review is presented here of the entire field of Russian applications of lasers in medicine and biology. Although the author, Dr. Gamaleya, has not worked directly with many of the applications, he has a general background in laser usage and has received much help from his colleagues in assembling the material. His review is restricted to Russian research. This does not mean that he is unaware of Western advances, rather that he has restricted his material to the parts that are peculiarly Russian or are significant confir mations of earlier work. Some of the Russian developments are quite novel and will certainly suggest to the careful reader new interpretations of old data, and possibly even new lines of research. The mechanisms proposed for the interaction of the high-intensity monochromatic light from lasers with biological material continue to grow in complexity.

The diversity of the chapters presented in this volume illustrates not only the many applications of lasers, but also the fact that, in many cases, these are not new uses of lasers, but rather improvements of laser techniques already widely accepted in both research and clinical situations. Biological reactions to some special aspects of laser exposure continue to show new effects, which have implications for the ever-present topic of laser safety. Such biological reactions are included in fields of research which depend on properties of electromagnetic radiation exposure only possible with lasers, for example, the short pulses necessary for the temperature-jump experiments reviewed by Reiss: Speciality lasers, such as the transverse excitation atmospheric (TEA) or excimer lasers, add new wavelengths and pulse domains to those already available for biological application. A description of these new types of lasers by Osgood is included to indicate new possibilities for future use and to avoid limiting our coverage to well-developed present-day applications. Hillenkamp and Kaufmann describe a microprobe mass spectrograph for analysis of the minute amounts of material evaporated by a laser pulse. The analytical possibilities of this instrument are far-reaching, and some of the various results are described to illustrate the power of their method, as well as to show the types of problems that are suitable for it. The initial steps in photosynthesis have become the subject of intensive investigation.

This book is a review of past and current studies and future plans of the Laser Laboratory in Cincinnati and some of the contributions of laser research groups in other medical centers. Special thanks are due to the Directing Physicist of the Laser Labora tory, R. James Rockwell. Without his advice, constant supervision and corrections, this enthusiastic investigator would continue to upset even many more people than he has done already. The excuse, of course, is to stimulate much needed interest and controlled research and development of the laser for biology and medicine. The Associate Research Physicist, Ralph Schooley, has worked with many phases of laser research but especially in Q spoiling, Raman spectroscopy, and the almost alchemy of holography. Holography, as of now, provides many opportunities for Gumperson's Law, "If anything can go wrong, it will. " Sincere appreciation is expressed to the Surgeons in the Laser Labora tory, who have supplied clinical and investigative surgical supervision often under great difficulties, Dr. V. E. Siler and Dr. Bruce Henderson. We are grateful for help from the Directing Biologist of the Laser Labo ratory, Edmond Ritter, the Director of Laser Neurosurgery, Dr. Thomas Brown and the Professor of Neurosurgery, Dr. Robert McLaurin, for important and basic work in laser neurosurgery. Special thanks are given to Robert Meyer, who has given most of the treatments in careful and skillful fashion, and his associate, Robert Otten.

This volume contains the lectures and seminars presented at the NATO Advanced Study Institute on Lasers in Biology and Medicine organized by the International School of Quantum Electronics at the Villa Le Pianore, Camaiore, Italy, August 19-31, 1979. Most laser applications in biology and medicine are highly interdisciplinary in nature, drawing from and pertaining to such diverse fields as the physical sciences ( (bio)physics, (bio)chemi stry) , engineering, the biological sciences (cellular research, photobiology) and finally theoretical and clinical medicine. Indeed the group of participants of the summer school did reflect this diversity both in background and interest. The presentations con tained in this volume mainly fall into two categories: tutorial lectures on the most important general subjects, intended to lay a common base for all participants, and a number of more advanced con tributions, serving the purpose of exemplifying selected but typical applications in their current state of development. Intense inter communication, lively discussion, and here and there even future cooperation were the general aims more than a detailed in-depth discussion of one or the other aspect of this large field. In this sense it is the hope of the organizing committee that, despite the inevitable limitations, a broad and reasonably representative cov erage of the field has been achieved and that this volume may be a valuable aid for newcomers to get a good start into this complex subject area for some years to corne.