CLINICAL METHODS AND INTERPRETATION OF THE RESULTS OF LASER DIAGNOSTICS
In accordance with the used general physical principles of optical noninvasive medical diagnostics, in the noninvasive medical spectrophotometry (NMS) the object of the medical investigation consists in evaluation of biochemical composition of human tissues including peripheral blood and lymph supply. The most easily "in vivo" detected biochemical components in tissues by optical techniques are: water, melanin, different fractions of hemoglobin (oxyhemoglobin, deoxyhemoglobin, etc.), lipids, porphyrins, as well as collagen and some other organic molecules. Dynamic fluctuations in peripheral blood microcirculation processes at a short scale of time allow a doctor to observe similar fluctuations in the registered concentration of one or another biochemical component, that makes it possible to diagnosis functional specialties of tissues' and vessels' clinical status (conditions). The changes in the registered parameters at a long scale of time allow a doctor to quantitatively study the efficacy of applied treatment procedures and tendencies in a patient's health. Therefore, such a noninvasive laser diagnostics (spectrophotometry) in medicine can be effective in its most diverse areas, from oncology and dermatology to occupational pathology, physiotherapy and other areas of medicine.
In terms of recording microhemodynamic parameters, the most easily recorded by the non-invasive biospectrophotometry are: the parameter of tissue perfusion with blood, parameters of some basic vascular fluctuations (vasomotions), especially heart rate and respiratory rhythms, which depend, among other things, on the elasticity of the walls of blood vessels, on the neuro-reflex and humoral regulation of peripheral blood circulation, as well as on parameters of oxygen transport and utilization in the microcirculation system, such as: arterial SaO2 and middle arteriovenous StO2 saturation of blood oxyhemoglobin in the microcirculatory bed of a cellular biological tissue, specific oxygen consumption by tissues (a parameter introduced by us) and a number of others. According to our data, the methods of non-invasive medical spectrophotometry (NMS) are the most informative when using various functional stress tests on the blood microcirculation system - an occlusion test, a drug test, a thermal test with local heating, etc. Functional tests generally have smaller errors and scatter of measurement results, allow one to standardize measurements, provide more information about the reactivity of the cardiovascular system and its reserves. In particular, with the help of the occlusion test, one can quite clearly, reproducibly and quickly obtain data on the type of microhemodynamics in a patient (normocirculatory type of microcirculation, angiospastic or hyperemic type of microcirculation) and on the basic vascular tone. It turns out, that at hypertension, patients do not always have an increased vascular tone (for more details, see here). Additionally, with the use of our reflectance oximeter "Spectrotest" it was shown in 2003 (see here our paper Tchernyi V.V., Rogatkin D.A. et. al. "Complex noninvasive spectrophotometry in examination of patients with vibration disease" // Proc. SPIE, vol. 6078, 2006. - pp.363-370) that there are various physiological rhythms in the StO2 parameter like ones exist in the blood perfusion which are measured by the Laser Doppler Flowmetry (LDF). So, the noninvasive spectrophotometry can be used in different areas of the modern medicine: surgery, oncology, urology, dermatology, radiology, gynecology, etc. for a purpose of better understanding of basic pathophysiological aspects of diseases. This opens up additional opportunities for functional diagnostics of the blood microcirculation system (BMCS). However, one must understand that the existing devices are still very far from perfect. The metrology and methods of such measurements are poorly developed. The errors of instruments and methods have not been studied. Therefore, a hasty interpretation of diagnostic results in medical terms is often fraught with errors. An example is the situation with devices and methods of LDF. This technology has existed for about 40 years, but is not used at all in practical medicine due to poor information content.
One of the most perspective area of applications of this diagnostic technique is the oncology. For oncology the overwhelming majority of the research and publications is concentrated now on a problem of the differential diagnosis of normal and malignant tissues for different localizations and clinical forms of young cancers. In our research we didn't obtain such promising results, but, meanwhile, in our opinion the noninvasive optical spectrophotometry can have high possibilities in monitoring an efficiency of different methods of tumors treatment, the radiotherapy and the chemo-radiotherapy, for instance. It is well known that different processes of blood microcirculation and tissues oxygenation in malignant tumors have a strong influence on a radiotherapy efficacy. But there are in the modern radiology only few methods to prognosticate a positive radiotherapy outcome. Noninvasive spectrophotometry can assist a doctor to produce a more objective and grounded prognosis by means of indicating a parameter of specific oxygen utilization in the malignant tissue, a parameter of blood perfusion in it, as well as different parameters of activity of cells' respiratory ferments in a tumorous area (see our paper in Photonics & Laser in Medicine here). In particular, in one of series of our experiments we found out a certain correlation between data of fluorescent diagnostics and the presence a chronic hypoxia state in tissues. It was done on the basis of registration of endogenous porphyrins fluorescence (see here and here). As the hypoxia is one of principal causes of radio resistance of tumors, determination of the oxygen status of a tumor "in situ" allows one to build an additional objective forecast for results of ionizing radiation treatment and soundly to appoint application to the patient of various radiosensitizers raising the maintenance of oxygen in cells of the tumor. Similarly, various inflammatory processes in the tissues are frequently accompanied by hypoxia. It allows using the methods of fluorescent spectroscopy in vivo to monitor the development of local inflammation in tissues and organs, including intraoperative monitoring. But in interpreting the results of fluorescence spectroscopy in vivo, a doctor needs to be very careful. The recorded signal depends on many parameters and non-linear depends on the relative concentration of fluorophores in the medium. Fluorescent data interpretation in terms of biochemical tissue composition is not a trivial task for the existed level of science. To read more - see our paper in Journal of Fluorescence (here).
Since approximately 2015, the main efforts of the laboratory staff have been focused on the development and testing of a new integrated non-invasive optical diagnostic technology, called "Technology"Vasotest"". This technology combines several methods for assessing central and peripheral hemodynamics, including a new method of incoherent optical fluctuation flowmetry (IOFF) developed by a laboratory employee, Ph.D. Denis Lapitan as part of his PhD thesis. It allows one to evaluate the basic vascular tone, the speed of propagation of the pulse wave, the reactivity of the microvascular bed, and many other parameters. To implement this technology, a prototype of a new diagnostic device based on an automatic blood pressure monitor was created (for more details, see here). Now a number of studies of the applicability and information content of the technology in endocrinology are being carried out in cardiovascular surgery, cardiology and other fields of medicine. Approximately 80% accuracy of the device in the detection of vascular lesions of lower extremities at diabetes mellitus, the sensitivity and specificity of the device in about 90% in the detection of hemodynamically significant stenoses of the arteries of the lower extremities, etc. has already been shown. Follow our publications on this issue in the relevant sections of our sites.