RU2549150C1 - Fractal flicker generator for biomedical investigations - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: generator comprises an external power supply with a connected microcontroller to two legs of which two n-channel field transistors are connected through L-shaped limiting ground resistors. Two or three light diodes and limiting resistors are connected to the above. Transistor drain circuits are grounded, whereas the generator is directly connected to a personal computer. Through it, pulse-width modulation legs of the microcontroller being integrated into the generator are programmed to vary the voltage by switching in and out the diodes at a required average brightness from 0.1 to 100 cd/m² for producing a fractal "sweep" pattern or a dichotomous pattern of doubled flicker packs. A flash length makes from 0.1 to 1 ms; a flash interval makes 0.1-1 ms; a flash number in one enclosure is from 3 to 7, and an enclosure number is from 2 to 6.

EFFECT: enables studying of the exposure on the living body parameters, including its visual functions, of a non-uniform light medium characterised by scaling time invariance.

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Description

The invention relates to the field of medical instrumentation and can be used in biomedical research.

The device is designed to generate a nonuniformly flickering background - a dynamic light fractal, in which fluctuations of the intervals between flashes are time-invariant.

Known random signal generators based on the conversion of natural fluctuations of an external or internal source into an electric signal [Bobnev MP Random signal generation. M .: Energy, 1971], the disadvantage of which is that the random signal is not fractal.

The known fractal signal generator [Kuznetsov A.P., Kuznetsov V.P. Fractal signal generator. Letters to ZhTF, 1992, v.18, N24, p.19], containing a sequential chain of counters associated with its bipolar, the principle of operation of which is based on recalculation of an iterative sequence of a certain type, as a result of which a signal with a fractional Hausdorff dimension appears at its output . The disadvantage of this fractal signal generator is the fact that it cannot receive signals with a Hausdorff dimension (D) greater than 1.

A known fractal signal generator, characterized in that a meander type signal generator with a fill factor of 0.5, N band-pass filters, N amplifiers with an adjustable gain and an analog signal adder [Kudasov Yu.B.; Makarova N.N .; Dubinov A.E. Fractal signal generator. Patent RU 2168848, 06/10/2001]. This generator solved the technical problem of creating a fractal signal generator with D> 1, which can be used to generate test signals simulating natural fractal signals, for example, signals from Langmuir probes in a plasma with structural turbulence.

The technical result of this well-known fractal signal generator is the possibility of using it to obtain fractal signals with a given Hausdorff dimension from the range 1 <D <2. This device is intended for the development of test generators in the metrology of fractal signals in the field of applied physics.

Existing generators of fractal signals are not intended to generate fractal light signals (flickers), in particular, for biomedical research.

At the same time, the absence of such devices is the main reason why the role of dynamic light fractals in biomedicine, including in the physiology of vision and ophthalmology, remains unexplored, which limits the knowledge about the dynamics of physiological processes that determine visual functions.

M.V. Zueva put forward a hypothesis about the dependence of the functional activity of the retina and the visual cortex on the effects of fractal light in normal and pathological conditions, and it was proposed for the first time to study the dynamics of the visual system of flickering light background with strictly defined nonlinear dynamics of interstimulus interval fluctuations (dynamic light fractal) [Zueva M.V. The dynamic fractal flickering as a tool in research of nonlinear dynamics of the evoked responses of a visual system and as the possible basis for new diagnostics and treatment of neurodegenerative disorders of the retina and brain. World Applied Sciences Journal (WASJ) 2013; 27 (4): 462-468].

The objective of the invention is the creation of a fractal flicker generator (GFM) for biomedical research.

The technical result of the proposed device is the ability to study the effects on the parameters of a living organism (and any biological object), including visual functions, of an inhomogeneous light medium having the property of scale invariance in time.

The technical result is achieved by generating a fractal sequence of flashes of a given structure using a device consisting of an external power source with a microcontroller connected to it, to two legs of which are connected two n-channel field-effect transistors connected to an L-shaped current-limiting grounding resistor, to which they are connected in series two and three LEDs and limiting resistors, the drain circuit of the transistors is grounded, the generator is connected directly to a personal computer, h the result of which the PWM legs of the microcontroller included in the generator are programmed with the possibility of changing the voltage by turning the diodes on and off to provide the necessary average brightness to obtain a dynamic fractal "sweep" pattern or dichotomous pattern of double flicker packs at specified flash parameters, their number in one attachment and the number attachments.

Biomedical Assignment

In accordance with the provisions of the hypothesis M.V. Zueva [Zueva M.V. The dynamic fractal flickering as a tool in research of nonlinear dynamics of the evoked responses of a visual system and as the possible basis for new diagnostics and treatment of neurodegenerative disorders of the retina and brain. World Applied Sciences Journal (WASJ) 2013; 27 (4): 462-468] GFM should provide a fractal sequence of flickers. The simplest example of a dynamic light fractal, by analogy with dichotomous branching in a geometric tree-like fractal, will be double bursts of pulses, each of which in its turn consists of a double burst of pulses, etc. (Figure 1). For nonlinear anatomical structures and the dynamics of physiological processes of biological objects, as a rule, the fractal dimension is in the range 1.2-3.

Considering that the effect of fractal light background on the visual system and brain activity has not been studied before, the range of the number of attachments from 2 to 4-6 should be provided for in the dynamic structure of flickers created by GFM.

In addition to the fundamental possibility of obtaining, using the proposed GFM, the dichotomous structure of fractal flickers, for implementation in the GFM we proposed a more complex dynamic fractal in which the sequence of events obeys the principle of “frequency sweep” known in physics - it can be called a dynamic “sweep” fractal (Figure 2 ) As noted in Fig. 2, in the first step there are n flashes, the duration of each flash is Tflash, the interval between flashes is successively reduced according to the linear law y = (ai) * x to the minimum value tmin, where y is the value of the interval between flashes, a - the number of flashes in the first step, i is the interval number, x is the minimum interval value (Figure 3).

The subsequent steps repeat this sequence at different time scales, instead of each flash we place the sequence of the previous step. To meet the optimal physiological parameters of light adaptation used in studies of the physiology of the visual system [Brigell M., Bach M., Barber C, Moskowitz A., Robson J. Guidelines for calibration of stimulus and recording parameters used in clinical electrophysiology of vision. Doc Ophthalmol. 2003; 107: 185-193; Holder GE, Brigell MG, Hawlina M., Meigen T., Vaegan, Bach M. ISCEV standard for clinical pattern electroretinography - 2007 update. Doc. Ophthalmol. 2007; 114: 111-116], the unit should at least provide an average brightness of the flickering background of 30 cd / m ² ± 10% and be able to change it in any given range in accordance with the objectives of the study (for biomedical research - from 0.1 to 100 cd / m ² ). However, at the same time, it should be possible to create any other brightness, pulse train, and control the average flicker brightness set by the researcher.

The value of the minimum interval Tmin is calculated based on the duration of the flash Tflash, the ratio m = Tflash / Tmin, the number of investments n and the maximum time Tmin + 2Δt. We take for the maximum time t = 1/25 s = 40 ms, where ν = 25 Hz (filming frequency). This frequency is enough to create a motion effect without noticeable stops to the eye.

To begin with, set the Tflash flash duration arbitrarily to 1 ms. Changing the number n, we calculate the value of the minimum interval Tmin for these parameters. During biomedical research, the minimum interval Tmin can vary between [0.1; 1] ms (Table 1). It should be possible to change the duration and number of outbreaks in one attachment and the number of attachments. The unit should exclude the possibility of electric shock of the biological object of research and personnel in the prescribed manner.

The proposed device, generating fractal flickering and providing control of the structure of the dynamic light fractal, consists of the software and hardware of the HFM. Figure 4 shows the electrical circuit of the GFM, the flicker dynamics in which is controlled by a computer program.

The HFM hardware consists of a microcontroller (1), current-limiting and grounding resistors (2, 3, 4, 5), two n-channel field effect transistors (6, 7), five LEDs (8, 9, 10, 11, 12), current-limiting resistors (13, 14) and an external power source not indicated in the diagram. Details of the GFM are fixed on the soldering board in accordance with the scheme. A microcontroller connected to an external power source is installed on the board, n-channel field-effect transistors are connected to two PWM legs of the microcontroller through connected L-shaped current-limiting and grounding resistors. In the drain circuit of transistor 6, three LEDs are connected in series (10, 11, 12). To limit the current and power, a limiting resistor (13) is installed in series with the diodes. Two LEDs (8, 9) and a limiting resistor (14) are connected in series to the drain circuit of transistor 7. Both working legs of the microcontroller with LEDs are connected to an external power source. The source circuits of the transistors are grounded. The developed unit is connected directly to a personal computer (PC). The microcontroller (MK) built into the unit is programmed through a PC so that the voltage on the output legs of the MK connected to the transistors changes, turning the diodes on and off and thereby creating a fractal pattern. We change the voltage at the legs of the microcontroller using a pulse-width modulation (PWM) generator, which is built into MK timers. Changing the duty cycle of the PWM (the ratio of the period to the pulse duration), you can smoothly change the output voltage, reaching a high and low level of illumination of a given fractal. The timer has a special OCR comparison register. When the value in the counting register of the timer reaches the value in the comparison register, the state of the external output of the comparison MK changes.

The program part of the GFM consists of two blocks: the main program (program body) and several subprograms: timer initialization subroutines for their use in PWM mode and subroutines written in the form of recursive functions describing the fractal embeddings.

The general principle of the program is presented in Fig.5. From the main program, the subroutine miganie4 (), which describes the last maximum attachment, is called in an infinite loop. From this subroutine, the miganie3 () subroutine is called, since each fourth-stage flash is a sequence of third-stage flashes. Similarly, from the miganie3 () routine, the smaller attachment routine miganie2 () is called, which refers to the miganie1 () routine. Since each attachment consists of four flashes, in each subprogram the previous attachment is called four times. In the main program, the timer initialization routine is called, the comparison counters are pre-reset, some MK legs are configured to exit, and the miganie4 () routine is called in an infinite loop.

The device operates as follows.

The experimental bioobject is placed at a calculated distance in front of the gas filter, mounted in a holder device of any design that meets the objectives of a particular study, electrodes or other sensors are connected to record certain physiological parameters before and after switching on the gas filter.

The GFM is adjusted to obtain the sequence of intervals between flashes, the duration of the stimulus, the number of flashes in one attachment, the number of iterations, and the given average brightness of fractal flickers necessary for each experiment to create a dynamic fractal "sweep" pattern or a dichotomous pattern of double flicker packs. The necessary physiological parameters are measured against the background of fractal flickering and / or after turning off the HFM, analyze the results obtained, comparing them with the results obtained under standard research conditions, and according to the analysis results, the effect of time-invariant fractal flickers is established on them.

For example, in electrophysiological (1), laboratory (2), histological (3) studies, biomedical studies are performed as follows:

(1) When studying electroretinograms (ERGs) and visual evoked cortical potentials (VEC) in a rabbit, rat, and other experimental animals, an active recording electrode in the form of a loop of silver or silver wire or in the form of a wick soaked in saline is placed on the cornea of the eye, and the reference and grounding electrodes in the form of thin needles are fixed subcutaneously on the scalp, when registering ERG and VECP in humans, the active electrode is placed on the cornea or behind the lower eyelid, the reference electrode is placed on the the outer edge of the orbit of the ipsilateral eye and grounding on the earlobe, then connect the recording electrodes to standard recording electrophysiological equipment, the GFM is fixed in the sphere of the ganzfeld photostimulator, turn on the GFM and adapt the eyes to the background of fractal flickers of the desired average brightness, after which they record various types of ERG and ZVKP before turning on, on the background and after turning off the HFM, analyze latency, the amplitude of their components, the frequency spectrum and other parameters, perform mathematical analysis and statistics matic data processing and compare the results with those obtained on a standard background light adaptation, compared to the results judged on the impact on the functional adaptation of retinal activity to fractal flicker.

A dynamic fractal should have a “sweep” structure, and when exposed to the retina in studies of the bioelectric activity of the retina and the brain, all fractal parameters calculated analytically and the high and low illumination values must comply with the ISCEV standards for optimal (physiologically adequate) background illumination for photopic recording of ERG L = 30 cd / m ² ± 10%. According to this standard, LEDs are selected for the electrical circuit, and in the software part it is necessary to maintain the fractal structural parameters as precisely as possible.

(2) When conducting biochemical, immunological and other laboratory tests, blood, tear fluid and other biological fluids are collected from an animal, human or other biological object before the GFM is turned on, during the exposure of the biological object to fractal flickers and after the GFM is turned off. The results are compared with the data obtained under standard research conditions and against the background of light adaptation to a uniform light background, and the results are used to judge the effect of fractal flickers on the studied parameters.

(3) When carrying out morphological intravital studies using optical coherence tomography or other morphometric imaging methods, as well as using a biopsy, the first studies are performed before exposure to fractal flickers, then the biological object is fixed in front of the GFM mounted in a device-holder of a design that corresponds to the research tasks, turn on the GFM and repeat the tests during the fractal adaptation process and after turning off the GFM; in post-mortem histological studies, tissue sampling is performed in different animals sequentially removed from the experiment at various times before and after exposure to fractal flickers. The results are compared with the data obtained under standard research conditions and against the background of light adaptation to a uniform light background, and the results are used to judge the effect of fractal flickers on the studied parameters.

Thus, the proposed device makes it possible to study the effect on the physiological (morphofunctional, biochemical, immunological and other) parameters of a living organism and the dynamics of the physiological processes of an inhomogeneous light medium having the property of scale invariance in time.

Claims (1)

A fractal flicker generator for biomedical research, consisting of an external power source with a microcontroller connected to it, to two legs of which two n-channel field effect transistors are connected through two connected L-shaped current-limiting grounding resistors, to which two and three LEDs and limiting resistors are connected in series, the transistor drain circuits are grounded, the generator is connected directly to a personal computer, through which the PWM legs of the microcontroller entering the generator miruyutsya able to change the voltage by turning on and off the diodes ensuring the necessary brightness from the average 0.1 to 100 cd / m ² to obtain dynamic fractal "sweep" sweep pattern or pattern dichotomous twin packs with the flicker duration flashes from 0.1 to 1 ms, the interval between flashes 0.1-1 ms, the number of flashes in one attachment from 3 to 7, the number of attachments from 2 to 6.

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