Laser applications in medicine and biology

It is fair to say that all metabolic processes are based on, or can be traced back to, chemical processes. By their very nature, however, many of them take place in the liquid or solid phase dictated by the cell structure in which they occur. On the other hand, many of the processes and reactions involve fundamental reactions exchanging gaseous specimens at the outer interface of a cell. An example is our respiration oxygen is extracted from the inhaled air and toxic exchange gases are expelled from the body during exhalation, e.g. one can smell in the breath of a person whether they have been drinking alcohol. 

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M. L. Wolbarsht (ed.). Laser Applications in Medicine and Biology, vols. 1-5 (Springer, Berlin, 1971-1991)... 

Figure 11 (A) Hemispherically shaped ends of fibres focus the output beam in air and coiiimate it in water. Adapted with permission from Rol P and Niederer P (1991) High-power iaser transmission through opticai fibres Appiications to ophthaimoiogy. in Woibarsht ML (ed) Laser Applications in Medicine and Biology, Voi 5, pp 141-198. New York Pienum. (B) Maximai irradiance is found at a distance of 3 times the fibre radius in water for quartz fibres with an NAof 0.2. The irradiance increases by a factor of 3.

Rol P and Niederer P (1991) High-power laser transmission through optical lihers Applications to Ophthalmology. In Wolharsht ML (ed) Laser Applications in Medicine and Biology Vol 5, pp 141-198. New York Plenum. 

The relevance of laser spectroscopy for numerous applications in physics, chemistry, biology, and medicine, or to environmental studies and technical problems has rapidly gained enormous significance. This is manifested by an increasing number of books and reviews. This chapter can only discuss some examples that are selected in order to demonstrate how many fascinating appUcations already exist and how much research and development is still needed. For a detailed representation of more examples, the reader is referred to the references given in the sections that follow as well as to some monographs and reviews [1358-1364]. 

The largest expansion of laser spectroscopy can be seen in its possible and already realized applications to chemical and biological problems and its use in medicine as a diagnostic tool and for therapy. Also, for the solution of technical problems, such as surface inspections, purity checks of samples or the analysis of the chemical composition of samples, laser spectroscopy has offered new techniques. 

In particular, the various applications of laser spectroscopy in physics, chemistry, biology, and medicine, and its contributions to the solutions of technical and environmental problems are remarkable. Therefore, a new edition of the book seemed necessary to account for at least part of these novel developments. Although it adheres to the concept of the first edition, several new spectroscopic techniques such as optothermal spectroscopy or velocity-modulation spectroscopy are added. 

Out of the vast number of applications in the field of medicine and biology involving laser chemical aspects, we are able to present only a handful of examples. One particularly interesting, now well-established, practical application is that of cancer treatment by photodynamic therapy (PDT), and all the monitoring processes around it examples are given in Sections 30.1 and 30.2. The analysis of the gases taken in and released in respiration is probably one of the most accessible fields for laser analytical techniques, and thus we discuss some relevant examples in Section 30.3. It has to be noted that the laser is used as an analytical tool here to add to the understanding of many of the fundamental processes in our metabolism the tech-... 

The book is divided into seven distinct parts and these are subdivided into individual chapters. In Parts I -3 we present the general principles that underpin the operation of lasers, the key properties of laser radiation, the main features of the various laser sources, and an overview of the most commonly used laser spectroscopic techniques, together with the instrumentation and methods for data acquisition. In Parts 4-6 we address the principles of unimolecular, bimolecular, cluster and surface reactions, which have been probed, stimulated or induced by laser radiation. In the final part, Part 7, we summarize a range of practical laser applications in industry, environmental studies, biology and medicine, many of which are already well established and in routine use. 

The application of laser spectroscopic methods to medicine and biology is only at the beginning of a rapid growth. The development of commercial tunable dye lasers in the ultraviolet region will certainly greatly enhance these applications. 

Instead of SNOM, in many cases, particularly if the sample is to be screened for Raman active spots and their spatial distance is more than half of the wavelength of the laser, it is also confocal Raman microscopy that delivers enough morphological and spectral information on both nanoparticle structure and SERS activity, respectively. Thus, confocal Raman microscopy is interesting for a wide variety of applications in biology, medicine, and technological materials research. 

The application of laser spectroscopy in biology and medicine gained a remarkable importance and is still rapidly growing. Some future aspects of biomolecular laser spectroscopy are already mentioned in the respective chapters. New technologies which combine lasers with conventional instruments, an optical mass spectrometer and a laser ion microscope are discussed by Letokhov 79). 

The power of laser ablation can be extended as a popular method for trace and bulk analysis in conjunction with ICP-OES and is an invaluable tool in the study of surface behaviour particularly where sensitive surfaces are important. The common area for surface knowledge is in environment, medicines, adhesives, powders, slurries, oil-based samples and liquids. It finds application in the analysis of metallurgical samples, non-conductive polymers, ceramic materials, surface mapping, elemental migration, depth profiling, thin film coatings, biological and clinical specimens, forensic, paint chips, inks, bullets, fabrics, etc. 

The laser scanning cytometer (LSC) is a microscope-based cytofluorometer that combines advantages of flow cytometry and image analysis and is finding wide applicability in many disciplines of biology and medicine (see reviews in refs. 8,9). LSC measures cell fluorescence rapidly and with similar accuracy as flow cytometer. However, since the xy coordi-... 

Recent advances in ultrasensitive instrumentation have allowed the detection of individual atoms and molecules in solids [174, 175], on surfaces [176, 177], and in the condensed phase [178, 179] using laser-induced fluorescence. In particular, single molecule detection in the condensed phase enables scientists to explore new frontiers in many scientific disciplines, such as chemistry, molecular biology, molecular medicine and nanostructure materials. There are several optical methods to study single molecules, the principles and application of which have been reviewed by Nie and Zare [180]. These methods are listed in Tab. 6.12. 

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