Possibilities of Laser Spectroscopy Methods for Prediction of the Radiotherapy Results

In this paper, possibilities of laser fluorescence spectroscopy to predict the reactions of the oral cavity cancer to radiation treatment are considered. A theoretically substantiated assumption about the link between the tumor’s consumption of an exogenous photosensitizer and its radioresistance is proposed. The first experience with the use of the Radahlorin photosensitizer is described; preliminary results of the 5 patients study are presented. As a result different photosensitizer consumptions versus different treatment outcomes are discussed. Keywords: laser fluorescence spectroscopy, photosensitizer, oral cavity cancer, radiotherapy, cross-resistanc

Лазерная флуоресцентная спектроскопия и оптическая тканевая оксиметрия в диагностике фиброза кожи

There are currently no effective measures to combat fibrosis in modern medical practice. One of the reasons for that is the late diagnosis associated with the lack of available clinical biomarkers and effective methods of non-invasive detection of the process. Fibrosis of the skin is characterized by fibrosis of the dermis, underlying tissues and is represented by a wide range of nosologies. Scleroderma and scars are of the greatest interest for the study. Skin changes in the development of bleomycin-induced fibrosis was studied in the experimental model using laser fluorescence spectroscopy and optical tissue oximetry. A significant increase in the rates of endogenous fluorescence of porphyrins, caused by inflammation and hypoxia, was detected at 7 and 21 days. An increased intensity of endogenous collagen fluorescence and a decreased specific oxygen uptake due to excess accumulation of the extracellular matrix were recorded on the 21st day after bleomycin treatment. Synchronous measurements of the collagen fluorescence and the specific oxygen uptake allowed to correlate the obtained data and the phases of the fibrogenic response described morphologically. The results allow to judge the severity of inflammation and hypoxia in the process of the fibrosis development. The objective and quantitative nature of the recorded parameters makes it possible to develop criteria for diagnosing the phases of fibrosis development.В современной медицинской практике нет эффективных мер борьбы с фиброзом. Одна из причин – поздняя диагностика, связанная с отсутствием доступных клинических биомаркеров и эффективных методов неинвазивного обнаружения этого процесса. Фиброзирующие заболевания кожи характеризуются фиброзом дермы, подлежащих тканей и представлены широким спектром нозологий. Наибольший интерес для изучения представляют склеродермия и рубцы кожи. На экспериментальной модели методами лазерной флуоресцентной спектроскопии и оптической тканевой оксиметрии изучены изменения кожи в рамках развития блеомицин-индуцированного фиброза. Выявлен достоверный рост показателей эндогенной флуоресценции порфиринов на 7 и на 21 сут, вызванный воспалением и гипоксией. Зафиксированы повышение интенсивности эндогенной флуоресценции коллагена и снижение показателей удельного потребления кислорода на 21 сут исследования, связанные с избыточным накоплением межклеточного матрикса. Синхронные измерения флуоресценции коллагена и удельного потребления кислорода позволили провести корреляцию с фазами фиброгенного ответа, описанного морфологически. Полученные результаты позволяют судить о выраженности воспаления и гипоксии в процессе развития фиброза. Объективный и количественный характер регистрируемых параметров дает возможность разработки критериев для диагностики фаз развития фиброза

A new look at fundamentals of the photometric light transport and scattering theory. Part 2:One-dimensional scattering with absorption

In the first part of the article, one-dimensional (1D) pure scattering processes were taken into detailed consideration. It allowed to prove that the scattering coefficient is not just a real optical property of a turbid medium, but also is a parameter of the mathematical description of the problem. It depends on the approximation, which is applied to solve the problem. Therefore, in different approaches it can vary. More real and close to realistic practical problems are scattering problems with absorption. This second part of the article describes the 1D scattering problems with absorption. It is shown, that scattering and absorption processes inside the light-scattering medium are not independent in most cases, so a formulation of the first coefficients of initial differential equations, which mathematically describe the problem, as the simplest superposition of scattering and absorption coefficients is wrong. Inaccuracy in this formulations leads to inaccuracies in final results. More correct formulation, for example, in application to the classical two-flux Kubelka - Munk (KM) approach, which is a good 1D limit for the radiative transport equation, allows one to obtain the exact analytical solution for boundary radiant fluxes (backscattered and transmitted ones), contrary to the classic KM approximation. In addition, it leads to the need for revision of definitions of a number of basic terms in the general radiative transport theory, especially of the albedo, which plays a key role in Monte-Carlo simulations.</p

A new look at fundamentals of the photometric light transport and scattering theory. Part 2:One-dimensional scattering with absorption

In the first part of the article, one-dimensional (1D) pure scattering processes were taken into detailed consideration. It allowed to prove that the scattering coefficient is not just a real optical property of a turbid medium, but also is a parameter of the mathematical description of the problem. It depends on the approximation, which is applied to solve the problem. Therefore, in different approaches it can vary. More real and close to realistic practical problems are scattering problems with absorption. This second part of the article describes the 1D scattering problems with absorption. It is shown, that scattering and absorption processes inside the light-scattering medium are not independent in most cases, so a formulation of the first coefficients of initial differential equations, which mathematically describe the problem, as the simplest superposition of scattering and absorption coefficients is wrong. Inaccuracy in this formulations leads to inaccuracies in final results. More correct formulation, for example, in application to the classical two-flux Kubelka - Munk (KM) approach, which is a good 1D limit for the radiative transport equation, allows one to obtain the exact analytical solution for boundary radiant fluxes (backscattered and transmitted ones), contrary to the classic KM approximation. In addition, it leads to the need for revision of definitions of a number of basic terms in the general radiative transport theory, especially of the albedo, which plays a key role in Monte-Carlo simulations.</p

FUNCTIONAL STUDIES ON BLOOD MICROCIRCULATION SYSTEM WITH LASER DOPPLER FLOWMETRY IN CLINICAL MEDICINE: PROBLEMS AND PROSPECTS

The paper presents a  review of the research update on the blood microcirculation system assessed with laser Doppler flowmetry (LDF). Specific procedures for measurement of the microcirculation index by LDF and individual variability of microcirculation parameters during their real time assessment in vivo are discussed. In physiological conditions, a relative deviation of the results of measurements by LDF is within the range±35% and above from the mean value of the microcirculation index. This imposes certain limitations on the interpretation of the diagnostic results in terms of the “normal or pathologic”. Specifics of performance of functional stress tests on the microcirculation system are reviewed. Diagnostic criteria based on functional stress testing of the microcirculation system, which can be implemented with methodologically strict normatives and regulations, for examples, those for the occlusion test, are more reliable from metrologic perspective and significant compared to the results obtained without stress testing. Problems of implementation of the functional tests into clinical practice are discussed. It was shown that they may have a potentially wide spectrum of clinical indications, from functional diagnostics and early detection of microcirculatory abnormalities in diabetes mellitus, arterial hypertension and other diseases associated with microcirculatory disorders, to the physical rationale of exposure parameters, as well as objectification of efficiency of medical procedures aimed to stimulation of the microcirculatory functions in a patient's tissues and organs

A new look at fundamentals of the photometric light transport and scattering theory. Part 1:One-dimensional pure scattering problems

In the majority of practical cases there exist difficulties with deriving an analytical closed-form solution of the classic radiative transport equation (RTE) in the light transport and scattering theory, which is widely used today in biomedical optics, ocean optics, atmospheric optics, etc. In our opinion, certain problems stem from the fact that the mathematical formulation of main physical processes at scattering in turbid media is not quite accurate. To study the problem in more detail, this paper once again describes and analyzes the photometric transport theory from the ''first phenomenological principles''. We show that this approach assists to clarify the problem in depth, as well as to obtain certain new, accurate and unexpected results. In this part 1 of the article, we consider in detail one-dimensional (1D) pure scattering problems featuring no absorption. We discuss and solve every main typical 1D pure scattering problem using various approaches. It allows us to prove that the scattering coefficient is not so much a real optical property of a turbid medium, but a parameter of the mathematical description of the problem. In the general case, the scattering coefficient depends on both optical properties of the medium and the mathematical approach selected. Therefore, it can vary with different approximations, which can be a source of errors in calculations.</p

A new look at fundamentals of the photometric light transport and scattering theory. Part 1:One-dimensional pure scattering problems

In the majority of practical cases there exist difficulties with deriving an analytical closed-form solution of the classic radiative transport equation (RTE) in the light transport and scattering theory, which is widely used today in biomedical optics, ocean optics, atmospheric optics, etc. In our opinion, certain problems stem from the fact that the mathematical formulation of main physical processes at scattering in turbid media is not quite accurate. To study the problem in more detail, this paper once again describes and analyzes the photometric transport theory from the ''first phenomenological principles''. We show that this approach assists to clarify the problem in depth, as well as to obtain certain new, accurate and unexpected results. In this part 1 of the article, we consider in detail one-dimensional (1D) pure scattering problems featuring no absorption. We discuss and solve every main typical 1D pure scattering problem using various approaches. It allows us to prove that the scattering coefficient is not so much a real optical property of a turbid medium, but a parameter of the mathematical description of the problem. In the general case, the scattering coefficient depends on both optical properties of the medium and the mathematical approach selected. Therefore, it can vary with different approximations, which can be a source of errors in calculations.</p

Optical non-invasive flowmetry without lasers and coherent light

Laser Doppler Flowmetry (LDF) and other optical technique to measure a blood flow in tissues noninvasively (in vivo) are well-known today. Meanwhile, in spite of more than 40-year history, they do not have applications in real clinical practice yet. This situation could be a consequence of incorrect understanding of the physical basics of these methods and, accordingly, of insufficient hardware design, software algorithms, as well as of erroneous interpretation of the data measured. The basic theory of physical principles of LDF is the model developed by R.Bonner and R.Nossal in 1980. However, it does not describe many phenomena, low-frequency fluctuations of optical fields due to a variable blood content in a tissue diagnostic volume, for example. In this study, we assumed that the low-frequency part of the power spectrum could provide the same information about the blood flow as the middle- and high-frequency parts provide it in LDF. Moreover, we proposed the use of coherent light source could be avoided in this case. We have developed a much simpler and low-cost LED-based prototype and confirmed our assumptions in experiments. Thus, we proposed a new technique to build simple and economic optical diagnostic tool to evaluate a blood flow in tissues.</p

Analysis of luminescence in turbid biological media

Background: Quantitative luminescent analysis is widely used in biology, laboratory diagnostics and clinical medicine to study objects at various levels. However, the existing simplified algorithms for calculation of the luminophore concentration in diluted linear solutions cannot be applied to the turbid media with strong light scattering, which include the majority of living biological tissues. Today, the development of luminescence analysis in medicine goes towards the creation of non-destructive and non-invasive methods of in vivo monitoring. Therefore, the urgent question is about a formulation of the research purpose and the development of algorithms to compute the luminophore concentration based on the luminescence spectra recorded in the turbid media. Objective: To formulate and justify the tasks of elaboration of the algorithms to compute the luminophore concentration based on the luminescence spectra recorded under conditions of the optically turbid media. Materials and methods: We looked upon the physico-mathematical simulation of the process of formation of the induced fluorescence emission in the light-scattering medium based on the modified 2-flux Kubelka-Munch model. We conducted a series of laboratory experiments with macro-homogenous light-scattering model media to determine characteristics of the dependence of the fluorescence intensity detected from the surface of an optically turbid biological medium upon the factor of light scattering and the concentration of the fluorophore in the medium. Results: Both theoretical and experimental results demonstrate complex nonlinear dependence of the fluorescence intensity detected upon the optical properties and a  concentration of a  fluorophore in the turbid media. This dependence is very different from the known linear  C.  Parker's solution for transparent media, which makes it impossible to use it in the optically turbid media. Conclusion: Further studies searching a  closed-form analytical solution of the inverse optical problem for light-scattering and fluorescent media are necessary to calculate the luminophore concentration in a light-scattering media based on the recorded luminescence spectra