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The first two parts of this book describe various theories associated with light propagation in tissue and the resulting response. If coherence or polarization information is not needed, we assume that the transport equation governs the optical interaction of light with tissue and the heat conduction equation provides the basis for estimating the thermal response of tissue to laser radiation. In part...
Optical fiber technology offers a convenient, affordable, safe and effective approach for the delivery and collection of light to and from the tissue region of interest, and has been employed clinically since the 1960s [1]. This chapter discusses and reviews the recent developments in optical fiber sensor technology in the field of biomedicine.
Seventy percent of our body is made up of water. For that reason, radiation based medical imaging techniques operate in spectral regions where water absorption is low (Fig. 18.1, left panel). Well known modalities are MRI that operates at radio frequencies, and PET/SPECT which work in the high frequency range. Water absorption is also low around the part of the spectrum that is visible to the human...
Photoacoustic tomography (PAT) refers to imaging that is based on the photoacoustic effect. Although the photoacoustic effect as a physical phenomenon was first reported on by Alexander Graham Bell in 1880 [1], PAT as an imaging technology was developed only after the advent of ultrasonic transducers, computers, and lasers [2–31]. A review on biomedical photoacoustics is available [32]. The motivation...
Light can react with tissue in different ways and provide information for identifying the physiological state of tissue or detecting the presence of disease. The light used to probe tissue does so in a non-intrusive manner and typically uses very low levels of light far below the requirements for therapeutic applications. The use of fiber optics simplifies the delivery and collection of this light...
For decades biological investigation has focused on a reductionist approach, which has greatly advanced our understanding of the biological process, but has also served to move the analysis further and further away from the living body. This was necessary as we sought to identify the cells, genes, mutations and/or etiological agents that were associated with a given process. The information generated...
Forensic medicine is a field of medicine where technology plays an increasingly important role in securing and evaluating evidence in, for example, child abuse cases and cases of domestic violence. Methods from chemistry and biological sciences have found a wide application within forensic medicine. Optical technologies like microscopy are also widely used. Despite this, in vivo or post mortem optical...
Port wine stain (PWS), also called nevus flammeus, is a congenital, cutaneous vascular malformation involving post-capillary venules which produce a light pink to red to dark-red-violet discoloration of human skin [1]. PWS occurs in an estimated 3 children per 1000 live births, affecting males and females and all racial groups equally [2]. There appears to be no hereditary predilection for PWS within...
Neural stimulation is the process of activating neurons using an external source to evoke action potential propagation down an axon. Electrical, chemical, thermal, optical, and mechanical methods have all been reported to stimulate neurons in both the central nervous system (CNS) and the peripheral nervous system (PNS) [1]. For nearly 2 centuries electrical stimulation has been the gold standard for...
Decades of effort understanding, inventing, designing, developing and using photothermal treatments for human disease have clearly improved medical care. Lasers are the treatment of choice for common eye, skin, upper airway, gynecological and venous disorders. The microscopic precision of laser tissue ablation and selective photothermolysis are unprecedented in medicine. Optical diagnostics have also...
The irradiation of tissue by laser light results in the absorption of energy. Since this is a fully dissipative process, the consequence is that the increment in energy is expressed entirely as a heat transfer absorbed by the tissue. In conjunction with this absorption, there will be an increase in the energy stored locally in the tissue as a function of the geometric pattern of absorption. Two primary...
The objective of this chapter is to present the fundamental mechanisms, instrumentation techniques, and error analyses for temperature measurements in laser irradiated biologic media. Because temperature is a significant biological parameter, it is important to understand and minimize potential measurement errors [1–8].
The transport of thermal energy in living tissue is a complex process involving multiple phenomenological mechanisms including conduction, convection, radiation, metabolism, evaporation, and phase change. There are three objectives of this chapter. First, the basic definitions of thermal properties and perfusion are presented. Second, experimental techniques to measure thermal properties and perfusion...
Heat is generated in laser irradiated tissues by absorption and transformation of the light energy into heat. Once generated within tissues, heat is heat no matter what original energy source is used to produce it. Heating of cells and biological tissues can produce reversible injury and dysfunction that can be repaired by innate cellular and host mechanisms. However, more severe, irreversible damage...
In this chapter we focus on the key elements that form our current understanding of the mechanisms of pulsed laser ablation of soft biological tissues. We present a conceptual framework providing mechanistic links between various ablation applications and the underlying thermodynamic and phase change processes [1]. We define pulsed laser ablation as the use of laser pulses with duration of ~1 ms or...
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