THE ENGINEERING BASIS OF CREATION OF THE EQUIPMENT FOR NMS
The development and design of the general engineering theory of diagnostic apparatus and systems for noninvasive laser medical diagnostics and spectrophotometry is an interesting and promising problem in the modern biomedical engineering. Being widely used and tested today in different countries, in different clinics and in different branches of medicine, these new medical equipment haven't got a fundamental engineering theory of projecting, constructions, simulations of them, etc. It is clear, that a common theoretical approach to creation of any medical, optics and/or electronic equipment is valid in this case as well. But it is also well known, that any new class of diagnostic equipment, especially medical, has its own specialties, which cause some specialties on all stages of the system's creation, from first stages of ideological-technical designing up to stages of development of system's software, methodological and metrological ware for that.
For this purpose in our study basing on the example of a multifunctional laser noninvasive diagnostic system (MLNDS) the scientific-engineering formalization of an object description of the problem was made. A tested biological object (BO) is supposed to be described as a nonlinear optical filter, coding the illuminating light (amplitude of its spectral components, pulses time delays, etc.) in accordance with the BO’s morphological and biochemical composition. So, the united target-function of MLNDS can be formulated as the decoding of a registered light from BO in terms of morphological and biochemical properties of the BO. Basing on that the structure-functional model of generalized MLNDS was developed. It was shown that five main functions must be executed by MLNDS’ hardware – an illumination of BO by known power of different wavelength light, the registration of a coded light from BO, the separation of that in two different arrays (low-power static optical signals in supplementary spectra and fast changed signals of initial spectra), the conversion of optical signals to electrical ones and the digitalization of electrical signals. All other functions can be executed now by up-to-date system’s software. Moreover, it was shown, that namely all possibilities of system’s software to calculate accurately any morphological and biochemical properties of BO dictate to designer a necessity of using of concrete wavebands, spectral power, time rate, etc., which all in total defines a systems' hardware architecture and specialties. So, it is grounded a key role of the system‘s software in all problems of architecture construction of MLNDS on the stage of its ideological-technical design. Additionally, the basic principles of block-modules composition of hardware of MLNDS were formulated in the study, as well. Almost all modules and hardware units of MLNDS can be constructed today as a standard blocks and modules which are produced by different companies and firms all over the World. So, the main function of a modern designer of MLNDS’ hardware consists in a synthesis of the system in a total with the use of standard, conventional and serial optoelectronic units and blocks. From the point of view of hardware, poorly studied remains the issues of proper selection of wavelengths, evaluation of sensitivity and linearity of the receiving channels of the equipment, and problems of specialized medico-technical requirements to them. See more in our publications (here, here and here)
More difficult and practically still a very poorly touched problem in scientific publications is the problem of metrology of measurements in NMS. If we say that NMS device allows to do for a doctor any conclusions about a state of health of the patient, allows to compare results, for example, two different measurements at two different patients or two different groups of patients, the first and the most important question is: "With which accuracy, reliability and reproducibility it can be done?". What errors of methods and devices exist in NMS? What their levels and occurrence sources? These and a number of other questions of metrology of NMS were investigated by us in 2008-2010 within the frames of the Russian Federal Basic Research Foundation grant No.08-02-00769a. Big physiological variability of the diagnostic data in NMS, a great influence of an interactive part of errors of measurements and a general level of the total measurement error reaching in some cases (even it has been as a result revealed at very qualified performance of measurements) up to 35-40% from measured value were estimated. Rather in detail all results of these researches are reflected in our articles of 2013 in the Measurement Technique magazine (see here: Part 1 "Physics and technology factors of errors"; Part 2 "Medicobiological factors of errors"). It means that use of NMS devices in clinical practice is problematic today in respect of statement and specification of the individual diagnosis. While they can be applied only as the scientific equipment for carrying out scientific researches and comparison of the examinees given in big groups (more 50 people) where individual variability of indicators is substantially averaged. Or it is necessary to develop techniques of carrying out measurements where average values in groups differ more than for 30% of their absolute values.