WO1998034099A1

WO1998034099A1 - A diagnostic method and a device for its implementation

Info

Publication number: WO1998034099A1
Application number: PCT/RU1997/000412
Authority: WO
Inventors: Gennady Mikhailovich Chernyakov; Vadim Dmitrievich Kudritsky; Alexei Fedorovich Balashov
Original assignee: Chernyakov Gennady Mikhailovic; Vadim Dmitrievich Kudritsky; Alexei Fedorovich Balashov
Priority date: 1997-01-30
Filing date: 1997-12-19
Publication date: 1998-08-06
Also published as: AU5580398A; RU2098016C1

Abstract

The present invention relates essentially to the art of experimental biology and physiology. The method involves generation of an SHF signal, splitting of the signal into a reference and measurement signals, exposure of an area of the specimen to the latter signal, and reception of the LF-frequency-modulated reflected signal. The resulting signal permits quantification of a status-indicative physical parameter of the specimen's area. To emit the signal, use is made of a circular cross section waveguide obturated by a set of dielectric discs. The phase of the measurement signal is shifted by an angle π and that of the reference signal, by an angle π/2, and the resulting signal is used to find the magnitude of integrated dielectric permittivity of the exposed area or the object as a whole. The device comprises an SHF oscillator, a 3 dB four-branch coupler, a measurement unit, waveguide transmission lines of the measurement and reference signals and phase modulators.

Description

A DIAGNOSTIC METHOD AND A DEVICE FOR ITS IMPLEMENTATION

Art The present invention relates essentially to the art of experimental biology and physiology and is particularly concerned with methods and devices for determining physical parameters of a study object, such as biological media, laboratory and farm animals and the like.

Prior Art

At present it is generally recognised that interaction of electromagnetic radiation with living organisms and biological media results in effects that yield vast diagnostic information. However, owing to imperfect knowledge of interaction mechanisms between electromagnetic radiation and biological objects, attempts to apply effects of exposure of biological tissues to electromagnetic radiation face challenging problems both in interpretation of findings and recording of these effects. The latter difficulty stems basically from the fundamental requirement that the measurement procedure be non-interfering with current metabolic processes.

Prior-art diagnostic procedures based on use of electromagnetic radiation include those involving recording of physical parameters of the study object (Ky3Heτj;oB A.H. BπoφH3Hκa 3JieκτpoMarHHTHtrx B03ΛeiιcτBHH., M., 3HeproaτoMH3flaτ, 1994 - Kuznetsov A. N., Biophysics of Electromagnetic Effects, Moscow, Energoatomizdat Publishers, 1994). These techniques, however, fail to provide a true picture of the actual status of the tissues because the recorded changes in their condition are presumed to result from electromagnetic exposure. In addition, both the procedures and the apparatus are cumbersome and inconvenient for online application.

Also known are diagnostic techniques involving recording of the reflected electromagnetic radiation flux in HF and SHF bands (tens and hundreds of MHz), whose magnitude is taken to be measure of physical parameters of the study object (Steel M., Sheppard R., Physics in Medicine and Biology, Vol. 33, No. 4, pp. 467-472.; Foster K. R., Schwan H. P., Dielectric properties of tissues // Handbook of Biological Effects of Electromagnetic Fields // Ed. C. Polk, E. Postow. Cleveland, CRC Press, 1987, pp. 32-96.). However, none of the suggested versions of waveguide, resonance or quasioptic methods are applicable for a wide range of biological studies owing to stringent requirements on the geometry and spatial fixation of the specimens.

A prior-art diagnostic technique, which is the closest to the one claimed herein, is the method involving generation of an SHF signal, splitting of the signal into a reference and a measurement signals, exposure of an area of the specimen to the latter signal, reception of the LF-frequency-modulated reflected signal, and comparison of the reference and reflected signals for developing a resulting signal, which is used to determine the status-indicating physical parameter of the study area (USSR Author's Certificate No. 1656475, 1991). Here only the phase of the reflected signal is measured; as a result, the information obtained is generally incomplete and sometimes is hardly reliable.

Another prior-art diagnostic device comprises a microwave oscillator whose output is connected to the first branch of a 3 dB four-branch coupler; the second branch of the coupler is connected to the measurement unit, the third, to the measurement signal waveguide transmission line, and the fourth, to the reference signal waveguide transmission line, both transmission lines being capable of fine adjustment of the signal path length, the measurement signal transmission line being provided with a radiation source, an appropriate modulator coupled to an audio oscillator, and both transmission lines being fitted with an appropriate short-circuiting switch (USSR Author's Certificate No. 1656475, 1991). This device is the closest to the one claimed herein, however, its disadvantages stemming from those of the respective technique fail to assure the required recording accuracy and data reliability.

Disclosure

An object of the present invention is to enhance the accuracy and reliability of proximate measurement of dielectric permittivity, an important physical parameter of a study object.

As regards the method, this object is attained through radiation of the signal via a set of dielectric rings which close the open end of the waveguide to make its characteristic wave impedance match that of the study specimen, the phase of the measurement signal being shifted by an angle π and that of the reference signal, by π/2, the resulting signal obtained by supeφosition of the reflected and reference signals being used to determine the overall dielectric permittivity of the exposed area of the specimen.

As regards the device, the above object is attained through provision of a circulator and arrangement of an appropriate waveguide transformer in each transmission line, the waveguide transformer of the reference signal line being connected between the coupler's fourth branch and the associated modulator, and the circulator being mounted on the measurement transmission line between the coupler's third branch and the radiation source and, in addition, connected via an appropriate waveguide transformer to the respective phase modulator, while the measurement unit comprising a square-law detector and a synchronous meter whose respective output is connected to that of the microwave oscillator and the radiation source being essentially a circular waveguide obturated by a set of dielectric disks.

It is important to point out that the thickness of the dielectric rings obturating the waveguide's open end does not exceed a half-wavelength in the dielectric which functions as the wave impedance transformer and is selected so as the dielectric disks minimise the difference in reflecting properties as the electromagnetic radiation passes from the waveguide to the tissue or medium under study.

Brief Description of the Drawings

Fig. 1 is a block diagram of the diagnostic device, i. e. an embodiment of the method.

A Preferred Embodiment

The device comprises a generator of radio frequency electromagnetic oscillations, for example, the microwave oscillator 1 ; a 3 dB directional coupler 2 with two frequency-isolated outputs (3) and (4); a square-law detector 3; a measurement signal waveguide transmission line made up by a radiation source 4, a circulator 5, a characteristic wave impedance transformer 6, a modulator 7 and a short-circuiting piston 8; a reference signal waveguide transmission line made up by a characteristic wave impedance transformer 9, a phase modulator 10 and a short-circuiting piston 11. The audio-frequency oscillator, for example, a low-frequency pulse master oscillator 12, is connected to the modulator 7 and to the appropriate input of the synchronous meter 13 (at the frequency of the master oscillator 12). The meter 13 and the detector 3 form the measurement unit. The output of the microwave oscillator is connected to the first branch (input 1) of the directional coupler 2 whose second branch (input 2) is connected to the input of the detector 3. The third branch (output 3) of the directional coupler is connected to the circulator, and the fourth branch (output 4), to the transformer 9, which is connected to the modulator 10 receiving the control current (not shown) from the short-circuiter (short-circuiting piston 11). The radiation source 4 of the measurement waveguide line is a circular waveguide obturated by a set of dielectric disks whose thickness does not exceed a half-wavelength in the dielectric material and which perform the function of characteristic wave impedance transformers and are selected so as to provide a good matching of the radiation source and the exposed surface of the test object. For instance, the radiation source can dielectric disks minimise the difference in reflecting properties as the electromagnetic radiation passes from the waveguide to the tissue or medium under study. For instance, the radiation source can be obturated by a quarter-wavelength man- made saphire disc which seals the waveguide opening and acts as a transformer lowering the dielectric permittivity of the material at its internal surface and reducing internal reflection. The remaining part of the reflected signal that was not compensated by the first disc is compensated by the second transformer made of, for example, a fluoroplastic plate whose parameters are selected to assure perfect matching. The plate is kept in place in the waveguide opening with the help of a foam plastic holder. With its field perfectly matched and synphased, the present radiation source has a lower field intensity at the edges, compared to a rectangular waveguide, which reduces boundary currents and enhances stability of the device's operation. The circulator 5 communicates via the transformer 6 to the modulator 7, which is connected, in its turn, to the short-circuiter (the short-circuiting piston 8). The transmission line formed by the circulator 5, the adjustable waveguide transformer 6, the modulator 7 and the short-circuiting piston 8 assures a phase shift of the signal by an angle π, while the phase-switching set-up comprising the adjustable waveguide transformer 9, the modulator 10 and the short-circuiting piston 11 shifts the phase of the signal by an angle π/2, both set-ups being capable of both positive and negative phase shifts. The method is implemented by the device as follows. Radio-frequency oscillations coming from the oscillator 1 are fed to the input 1 of the 3 dB directional coupler 2 and transmitted via the input 3 and 4 to the measurement and reference signal transmission lines. The measurement signal is transmitted over its line by the circulator 5 to the reflected-signal phase modulator which is made up by the characteristic wave impedance transformer 6, the modulator 7 and the piston 8. The transformer 6 is tuned, and the position of the piston 8 adjusted so that with the control voltage on the master oscillator 12 modified, the reflected signal level on the modulator remains unchanged but the phase of the signal is shifted by the angle π. The phase modulation of the measurement signal is controlled by low-frequency voltage of the master oscillator 12. The modulated signal is fed via the circulator 5 to the radiation source 4, interacts with the study object and gets reflected, again via the circulator 5, to the directional coupler 2. The reference signal is reflected from the phase switch made up by the transformer 9, the modulator 10 and the piston 11 and adjusted so that with the control voltage on the modulator 10 modified by an external or internal control unit not shown in the diagram, the reflected signal level on the modulator remains unchanged but the phase of the signal is shifted by the angle π/2. The reflected measurement and reference signals are summed in the directional coupler 2 and fed into the square-law detector whose output signal is measured by the synchronous meter 13. Depending on the position of the reference signal phase shifter, which is mounted on the modulator 10, measurement findings correspond to the actual or imaginary component of the measured physical parameter, i.e. the integrated microwave signal reflection factor, which is used for on-line automatic computation of the sought physical parameter, i.e. dielectric permittivity of the study object.

Studies were carried out using a circular radiation source with a quarter-wavelength man-made saphire disc, which optimised monochromacity of the reflected signal. The test radiation frequency was 30 GHz, while the density of the radiation flux interacting with the specimen was within 5 μW ^■ cm^" .

The range of biological tissues and media whose dielectric permittivity can be measured is limited substantially by the requirement that specimens be basically homogeneous within the planar zone of contact with the radiation source and within the radiation penetration depth. This requirement is fully met by such media as bile, urine, blood plasma and the like. When measurements were made to establish relative changes in the condition of a test object this homogeneity requirement was not as stringent. Such measurements are totally acceptable for skin and skin transplants in monitoring of their functional status through the magnitude of the amplitude and the phase of reflected signals without conversion to dielectric permittivity components.

Laboratory animal studies demonstrated the amplitude and the phase of reflected signals of the above-stated frequency range to be highly sensitive to changes in the state of a biological object. In particular, untoward trends of the functional condition of skin transplants, which could be recorded by conventional histological, histochemical and biochemical methods 72 hours after the transplantation or later, were positively revealed through analysis of the parameters of reflected electromagnetic radiation as early as 18 to 25 hours. Human B-bile studies showed the magnitude of the imaginary component of integrated dielectric permittivity to be a lithogenesis criterion. When this parameter exceeds 19, bile is not lithogenetic, and the patient is healthy in terms of no formation of calculi in the bile cyst.

With the parameter under 17 a progressing lithogeny can be diagnosed with certainty. Bile conditions showing 18.5 < ε " > 17.5 are a very good reason to suspect an early stage of formation of calculi in the bile cyst. The above-quoted values are obviously valid only for the frequency range of electromagnetic radiation that was applied in the tests under discussion. Similar measurements with different devices will yield different quantities.

Tests on dogs indicated that the magnitude of ε " for the erythrocyte mass of blood makes it possible to distinguish between a normal and an endotoxic condition of animals with a probability of 99.9% or better. This diagnostic technique was checked in clinic tests of an extracorporal hemacorrection monitoring system.

Seeing a sufficient structural homogeneity of urine, its lithogeny diagnosis can be soundly based on values of integrated dielectric permittivity; however, a more convenient approach is to use the directly measured amplitude and phase of the reflected signals because of an insignificant difference between healthy and lithogenic native urine. By contrast, certain manipulations, such as vacuum concentration, can noticeably emphasise this difference. A reliable diagnostic feature is not so much the recorded electrodynamic parameters but the rate of their change after an additional laboratory procedure, such as concentration.

Industrial Applicability Application of the proposed method and device makes it possible to record effectively electrodynamic characteristics of a large range of native objects of biological origin, including food products, cosmetic items etc. Of greatest interest here are natural and artificial products whose quality depends on their colloid state parameters, such as milk, gels, suspensions etc.

A small size of the device and its reliable performance in unfriendly mechanical and thermal environments permit application of the method both in laboratory and in the field without no concern about accuracy or reliability of the data obtained. It is highly consequential that a measurement takes as little as a few seconds, with real-time further presentation of the results.

Claims

WHAT I CLAIM IS:

1. The diagnostic method involving generation of an SHF signal, splitting of the signal into a reference and a measurement signals, exposure of an area of the specimen to the latter signal, reception of the LF-frequency-modulated reflected signal, and comparison of the reference and reflected signals for developing a resulting signal, which is further used to determine the status-indicating physical parameter of the study area of the object, characterised in that the signal is emitted using a circular cross-section waveguide obturated by a set of dielectric discs, the phase of the measurement signal being shifted by an angle ╧Ç and that of the reference signal, by an angle ╧Ç/2, and the resulting signal being used to determine the magnitude of the integrated dielectric permittivity of the study area of the object or of the entire object.

2. A diagnostic device comprising a microwave oscillator, its output being connected to the first branch of a 3 dB four-branch directional coupler whose second branch is connected to the measurement unit, the third, to the measurement signal waveguide transmission line, and the fourth, to the reference signal waveguide transmission line provided with a phase modulator, the two transmission lines being capable of fine adjustment of the signal path length, the measurement signal transmission line being provided with a radiation source, an appropriate modulator coupled to an audio-frequency oscillator, and both transmission lines being fitted with an appropriate short-circuiting switch, characterised in that the device is provided with a circulator and that each transmission line is provided with a waveguide transformer, that of the reference signal line being connected between the fourth branch of the coupler and the respective modulator, while the measurement signal line has the circulator connected between the third branch of the coupler and the radiation source and also connected via the respective waveguide transformer to the respective phase modulator, the measurement unit comprising a square-law detector and a synchronous meter whose appropriate input is connected to the output of the audio-frequency oscillator, while the radiation source is a circular cross-section waveguide obturated by a set of dielectric discs.