Biomedical Aspects Of The Laser

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.

The laser's range of application is extraordinary. Arthur Schawlow says, "What instrument can shuck a bucket of oysters, correct typing errors, fuse atoms, lay a straight line for a garden bed, repair detached retinas, and drill holes in dia monds?"O The laser's specifically biomedical uses cover a similarly broad and interesting spectrum. In this book, I have endeavored to convey some of the fas cination that the laser has long held for me. It is my hope that both clinicians and researchers in the various medical and surgical specialties will find the book a use ful introduction. Biologists, particularly molecular biologists, should also find a great deal of relevant information herein. This volume's distinguished contributors provide admirably lucid discussions of laser principles, instrumentation, and current practice in their respective special ties. Safety, design, capabilities, and costs of various lasers are also reviewed. We have aimed to create a practical text that is comprehensive but not exhaustive. Our emphasis on the practical, rather than the esoteric, is dictated not only by the short history of biomedical laser use, but by the extent of the community to which this information will appeal.

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.

Basic concepts such as the optical and thermal properties of tissue, the various types of tissue ablation, and optical breakdown and its related effects are treated in detail. Special attention is given to mathematical tools (Monte Carlo simulations, the Kubelka—Munk theory etc.) and approved techniques (photodynamic therapy, laser-induced interstitial thermotherapy etc.). The part on applications reviews clinically relevant methods in modern medicine using the latest references. The last chapter covers today’s standards of laser safety, with a careful selection of essential guidelines published by the Laser Institute of America. With numerous research photographs, illustrations, tables and comprehensive summaries.

This book presents practical information on the clinical applications of short pulse laser systems and the techniques for optimizing these applications in a manner that will be relevant to a broad audience, including engineering and medical students as well as researchers, clinicians, and technicians. Short pulse laser systems are useful for both subsurface tissue imaging and laser induced thermal therapy (LITT), which hold great promise in cancer diagnostics and treatment. Such laser systems may be used alone or in combination with optically active nanoparticles specifically administered to the tissues of interest for enhanced contrast in imaging and precise heating during LITT. Mathematical and computational models of short pulse laser-tissue interactions that consider the transient radiative transport equation coupled with a bio-heat equation considering the initial transients of laser heating were developed to analyze the laser-tissue interaction during imaging and therapy. Experiments were first performed to characterize the tissue optical properties needed to optimize the dose for thermal therapy. Experiments were then performed on animal models to characterize the heat affected zone for LITT. The experimental measurements were also validated using the computational models.