Method for recognizing an object during laser lithotripsy

Abstract

The invention relates to medicine. Claimed is a method for recognizing an object inside an organism, more specifically a stone and / or soft tissue (flesh), following digital processing of a light signal by analysis of the algebraic sum of characteristic regions thereof. Optical signals in a wavelength range of 540-630 nm are processed, and, on at least two wavelengths, criteria for determining the presence of a stone in the aperture of a laser fibre are calculated as the algebraic sum of validated optical signals. According to the sign of the sum, an object is identified as a stone and / or flesh. The technical result is that of enabling safer use of a laser during real-time lithotripsy, while minimizing the possibility of damage to the soft tissues, and enabling a more efficient technique for fragmenting stones by allowing a laser beam to be more reliably aimed at a stone following digital processing of the light signal reflected thereby, using the proposed criteria.

Description

[0001] METHOD OF OBJECT RECOGNITION IN LASER LITHOTRIPSY

[0002] Field of technology

[0003] The invention relates to methods for recognizing an object in the body based on the spectrum of reflection of electromagnetic radiation by the object, namely light, wherein the object is recognized in surgical laser lithotripsy operations, namely a stone and / or soft tissue (flesh), after numerical processing of the light signal based on an analysis of the algebraic sum of its characteristic sections.

[0004] Prior art

[0005] When performing laser endoscopic lithotripsy surgery, the problem area is always not only the visual observation of the surgical site by the surgeon, but also the method of protecting soft tissues from unwanted effects of laser radiation when the beam is not accurately aimed at the stone. Therefore, much attention is paid to the method of recognizing the object, and certain algorithms are developed to reliably aim the laser beam at the object to be destroyed - a calculus, for example, in the form of a stone. In addition, in addition to the telemetry information that the surgeon has, visually observing the object, the identification algorithms duplicate the visual channel and contribute to more accurate aiming at the calculus and thereby reduce the area of ​​damage to soft tissues in the surgical area.When using laser radiation in surgical operations to defragment stones in the bladder, ureters, kidneys, or in the bile ducts and gall bladder, one of the main principles is the preservation of healthy soft tissues in the area of ​​laser exposure. The destruction of the stone is achieved by absorbing the energy of laser radiation, while it is desirable to minimize the impact on adjacent soft tissues.

[0006] Spectral analysis of light reflected by an object can provide information on both its scattering and absorption properties. The main absorbers in most soft biological tissues are oxyhemoglobin (HbO2), deoxyhemoglobin (Hb), water, and lipids. The absorption spectral regions of oxyhemoglobin (11=542 nm, 12=577 nm) and deoxyhemoglobin (1=555 nm) play a dominant role in the analysis of optical spectra. Hemoglobin is one of the main chromophores in the visible region of the spectrum in most tissues of the mucous membranes, including tissues of various parts of the urinary tract (bladder, ureter, kidney), while stones do not contain hemoglobin. Thus, by the presence of light absorption in the region of the specified wavelengths in the spectra of reflected light, it is possible to identify the illuminated object and recognize hard tissue surrounded by soft tissue.

[0007] A method of contact laser lithotripsy is known. In particular, this method combines the endoscopic method of removing kidney stones and laser therapy. The endoscope is inserted through the urethra and ureter to the stone. After that, the laser is activated, which allows both fragmenting and spraying stones with high efficiency, regardless of their density and composition. However, damage to soft tissues in the area of ​​exposure is an extremely undesirable side effect. The degree of damage to soft tissues during laser irradiation is determined by its power, wavelength and duration of exposure to pulsed or continuous laser operation. Holmium and thulium lasers with a wavelength of about 2 microns have proven themselves to be the best. The depth of penetration of such radiation into soft tissues is tens of fractions of a millimeter. This is determined by the fact that soft tissues contain water - the main absorber of radiation with a wavelength of 2 microns.On the other hand, if laser radiation with a wavelength of about 1 μm is used, the penetration depth increases significantly to 1 cm, which can lead to deep tissue damage. The accuracy of targeting the irradiation object - the stone - plays an important role. As a rule, external monitoring (for example, ultrasound or direct video surveillance from a video device built into the endoscope) is used to visualize and target the fiber optic emitter directed and fed to the stone. After visualizing the stone, it is irradiated with laser radiation, which achieves its fragmentation as a result of absorption of laser energy. However, such a procedure depends on the skills of the personnel and does not exclude the accidental factor of soft tissue damage, which is a significant drawback of the procedure.

[0008] A method for fragmenting kidney stones using a femtosecond laser is proposed: US 20110218524A1, Giorgio CATTANEO, METHOD AND APPARATUS FOR LASER-BASED SURGERY AND TREATMENT. The author claims that laser pulses up to 100 fs long do not cause side effects or soft tissue burns due to the short exposure time. This statement is generally incorrect. The extent of damage is largely determined by the laser wavelength and pulse power, or more precisely, the depth of penetration into soft tissue, as indicated above. Optical feedback is used to accurately guide the emitter in the form of an objective with a movable lens to focus the radiation. In this case, part of the radiation reflected from the stone or soft tissue gets back into the objective and is analyzed on a spectrophotometer. The author claims that the wavelength of the reflected radiation depends on the chemical composition of the reflecting object.Therefore, by analyzing the reflection spectrum characteristic of the irradiated solid object, we can reliably assert that the lens is aimed where it should be, based on the analysis of the chemical composition of the object. But in order not to damage the tissue during the spectral analysis, its illumination is carried out at a reduced laser radiation power and focusing the radiation using a movable optical system of lenses. The disadvantage of this method is the need to rebuild the laser using control equipment, and this must be done after each powerful pulse, which is a complex and non-optimal procedure from a technical point of view. In addition, irradiation of soft tissues with laser radiation even at a reduced power can cause damage to it. The degree of reliability of the laser beam guidance to the stone is not even discussed.

[0009] In the publication US2021 / 0038304 (A1) — Systems, devices and methods for identifying various types of structures with different compositions in vivo and accordingly adjusting the power of a surgical laser in a medical lithotripsy procedure are disclosed. The laser processing system comprises a laser system configured to generate a laser beam for delivery to a target in the body - a calculus, and a controller circuit configured to receive a light signal reflected from the target, generated, in particular, by a light source. One or more spectroscopic properties are analyzed from the reflected signal, without specifying which one. The laser system can be controlled to operate in an operating mode based on target identification. However, the authors do not provide a criterion for the reliability of stone recognition in the aperture of the laser fiber and, especially, in the presence of soft tissue.

[0010] Therefore, the development of a minimally invasive, safe laser method for defragmenting stones in the body with a reliable system for identifying the irradiated object, which does not require complex spectral analysis of reflected radiation and increases the safe use of the laser, is an important and urgent task.

[0011] The proposed invention is free from the above-mentioned disadvantages.

[0012] Disclosure of invention

[0013] The objective of the present invention is to increase the safety of laser lithotripsy due to the applied criterion of stone recognition in the laser beam aperture during a surgical operation. In this case, the technical result is achieved - increased safety of laser use in lithotripsy in real time while minimizing the possibility of damage to soft tissues, and achieving higher efficiency of the stone defragmentation technique due to more reliable guidance of the laser beam to the stone after numerical processing of the light signal reflected from it based on the proposed criterion.

[0014] The invention proposes a method for recognizing an object - a stone and / or soft biological tissue during a surgical laser lithotripsy operation, consisting of analyzing the light reflected from them from the source used, characterized in that the reflected light is received by means of a laser fiber aimed at the object in the absence of laser radiation, the levels of light reflected from the object are recorded at least at two wavelengths I (.4 1) and 1 (Ya 2) and their normalized values ​​are calculated in relation to the previously measured light levels, at the corresponding wavelengths. And 1 С(Л2) of the mentioned source when reflected from the reference body before the operation, as the logarithm of their ratio i*(Af)= ig (1(Л / 1оОО), (1) where J =1-2 is the ordinal number of the wavelength A, ; then, to separate objects into two classes: stone or soft tissue, an algorithm for processing data of the type (1) is used according to a certain criterion for recognizing a stone in the aperture of a laser fiber, based on a comparison of the weight terms of the algebraic sum of the normalized signals (1): Where , c - weight numerical coefficients; if this condition is met, then the fiber is directed to the soft tissue, if not - to the stone.

[0015] Other advantages and distinctive features of the proposed invention will become apparent from the following description of preferred embodiments thereof, given with reference to the accompanying drawings, which are illustrated below in the figures and in their brief description.

[0016] Brief description of the drawings

[0017] Fig. 1. Scheme of receiving back-reflected light 2 from object 10 by laser fiber 4 when illuminated by light source 3 in the area of ​​surgical laser exposure 11.

[0018] Fig. 2. Schematic representation of endoscope 9 with surgical laser fiber 4.

[0019] Fig. 3. Initial optical spectra of light reflected from an object on a logarithmic scale: 12 - spectrum of the light source (illuminator), 13 - spectrum of light reflected from a stone, 14 - spectrum of light reflected from soft tissue.

[0020] Fig. 4. Normalized spectra from object I* in relation to the spectrum of illuminator 1o of fixed power (illumination level):

[0021] 15 - normalized spectrum of light reflection from stone, 16 - normalized spectrum of light reflection from flesh,

[0022] 17 - normalized spectrum of light reflection from stone and flesh in equal proportions present in the aperture of the laser fiber.

[0023] Implementation of the invention

[0024] Fig. 1 shows an object 1 under the action of irradiated light 2 emitted by a fiber light guide 3 from a source 5, when the laser radiation formed by a laser 6 and delivered via a fiber 4 is switched off. In the absence of laser radiation, the light reflected from the object 1 via the laser fiber 4, entering the aperture of the laser fiber, enters the spectral photodetector (spectralizer) 7 and then into the controller 8, coupled with a digital programmable computing device for processing data according to the adopted algorithm by calculating the criterion (2). After such processing, the controller 8 receives a control command to turn the laser on or off. This command duplicates the visualization of the stone 10 (Fig. 2) by the surgeon and helps him to minimize the area 11 of surgical damage to the soft tissue in the vicinity of the stone.

[0025] It is essential that a source with a continuous spectrum in the wavelength ranges of criterion (2) is used as the light source 5. An example of such a spectrum 12 is shown in Fig. 3. The source can be made on the basis of LEDs of sufficiently high brightness, which will have a positive effect on the signal / noise ratio of the light signal received by the photodetector.

[0026] The algorithm for recognizing an object involves determining the weighting numerical coefficients of criterion (2). The regions of the absorption spectra of oxyhemoglobin (AD=542 nm, 2=577 nm) and deoxyhemoglobin ( / =555 nm), which play a dominant role in the analysis of optical spectra, as well as the adjacent region of intense light reflection from a stone of 600-630 nm, are best suited for this purpose. For the case when two wavelengths, L1 and L2, are used in the analysis, the numerical coefficients are found empirically (or using known linear regression methods [1]) when modeling on a reference object in laboratory conditions, when it is illuminated by a source with a spectrum similar to the spectrum of the source in a surgical instrument. The object can be a surface of, for example, frosted glass or Teflon. For those shown in Fig. 1 spectra the following weighting numerical coefficients are set for two wavelengths: 575±5 and 600±5 nm, and the corresponding weighting coefficients: D €{575, 600}, , W S7S = +1, C = -0 / 13.

[0027] Obviously, by the property of any inequality they can be changed proportionally by multiplying by any real number except zero.

[0028] It is essential that criterion (2) is calculated in the wavelength range: 540-630 nm. It is essential that in the specified wavelength range, criterion (2) is calculated at two wavelengths: 575±5 and 600±5 nm and the corresponding weighting numerical coefficients, for example:

[0029] Xi £{575, 600}, c = — 0.15.

[0030] During the surgical operation on lithotripsy, the presence of a stone in the aperture of the laser fiber is diagnosed. For this purpose, reflected light is received via the laser fiber 4 when the object is illuminated by the light source 5. The level of reflected light is measured by a spectral photodetector (spectrophotometer or selective photodiodes) 7 at at least two selected wavelengths. Then, the ratios (1) are calculated and, according to the criterion (2), it is established which object the laser fiber is aimed at - the stone or soft tissue. If at the stone, then the laser can be turned on and destroyed. If at the tissue, then the surgeon decides this based on the circumstances of the operation (the stone may need to be freed from the flesh covering it). In this case, the surgeon can turn off this protection system.

[0031] To find weight coefficients for three or more wavelengths, it is convenient to use mathematical probabilistic methods of classifying two classes of an object, for example, the logistic regression method [1]. Logistic regression calculates the probability that a given initial value belongs to a certain class. It is used for classification problems: it estimates the posterior probabilities of a given object belonging to a particular class (soft tissue or stone). Then, if you select a threshold for the probability of belonging to one of the classes (usually 50%), the boundary between the classes will be described by a hyperplane, the equation of which will be specified by the regression coefficients, that is, the weight numerical coefficients in criterion (2).

[0032] Before the practical application of the technique in surgery on a patient, a laboratory simulation of the situation is carried out on a model in order to find characteristic wavelengths and classify the object. Then, by collecting and processing data from light signals from objects in various surgical operations, in order to expand possible situations, an additional correction of the recognition algorithm is carried out and the numerical parameters of the criterion (2) for diagnosing a stone or soft tissue are specified.

[0033] It is also significant that as a result of a similar procedure for criterion (2), a set of three analyzed wavelengths in the ranges of 550±5, 575±5 and 600±5 nm and the corresponding numerical parameters were established, for example: i £{550, 575, 600}, +1, w 600 = -0.025, s = -0.025

[0034] The algorithm described above, when implemented in a computing device, allows one to calculate criterion (2) based on the measured optical signals I* (1) and to determine the type of object in the aperture of the laser fiber based on the sign of its numerical value: stone - negative value of criterion (2), soft tissue - positive. Tables 1 and 2 show the results of calculating criterion (2) for the data of the light reflection spectra presented in Fig. 4 (initial 12-14, Fig. 3). As can be seen from the tables in this example, when reflecting light containing 10% of light from a stone and 90% from flesh, this algorithm recognizes the object as a stone.

[0035] Table 1

[0036] Table 2

[0037] Example of implementation of the invention.

[0038] The method was tested using a thulium quasi-continuous laser with a power of up to 60 W and a wavelength of 1.93 μm (FiberLase U2, NTO "IRE-Polus", RF)

[0039] (https: / / www.ipgphotonics.eom / m / 182 / FileAttachment / FiberLaseHJ2.pdf) This laser is used in rigid and flexible ureteronephroscopy, percutaneous, minipercutaneous, ultraminipercutaneous and micropercutaneous surgeries. The device is easily integrated into an endoscopic stand, having a small weight and dimensions. The new superpulse mode of the thulium fiber laser allows both fragmentation and dispersion of stones with high efficiency, regardless of their density and composition.

[0040] Initially, in laboratory conditions, optical spectra were measured using a spectrum analyzer, the output signal from which was digitized and programmatically processed according to the algorithm described above.

[0041] After establishing the characteristic sections of the spectrum in the wavelength range of 540 - 630 nm of light absorption by blood components in the flesh, as well as in the region of 575 - 630 nm of intense light reflection by the stone, two and three wavelengths were determined for the optimal calculation of criterion (2), indicated in Tables 1 and 2. Then, for these sets of wavelengths, synchronous reception of light reflected back from the object was carried out by means of selective photodetectors at the established wavelengths, and criterion (2) was calculated by means of their digital processing. Then a command to control the laser switching on was formed when its value was negative. The developed procedure allows, at the surgeon's discretion, to block the command to switch on the laser when working on soft tissue or to activate its protection against accidental laser activation when pointing beyond the stone - at the flesh.

[0042] In a real surgical setup, the role of the spectrometer is performed by selective fiber filters for each of the 2 or 3 wavelengths. This increases the speed of response during a real operation. The reflected light signals, having passed these filters, are received by photodetectors, converted into electrical signals and then processed in a programmable microcontroller according to the algorithm specified in the invention formula. Criterion (2) is calculated, which can be greater or less than zero. The type of function I*, which is shown in Fig. 4, and the tabular data are indicated for urological stones. Somewhat different dependencies will be for gallstones or salivary stones, but the main thing is that the criterion of targeting pure 100% soft tissue will remain unchanged and positive, whereas otherwise, any deviation of the criterion to the negative side due to the light reflected from a foreign formation entering the aperture of the laser fiber will indicate the presence of a stone.

[0043] The invention can be used in laser lithotripsy in minimally invasive operations, for more precise targeting of the laser fiber on the stone and for increasing the safety of using laser radiation with minimization of the undesirable impact of laser radiation on soft tissues.

[0044] The method is currently undergoing multi-clinical studies in three medical institutions, where the tissue type sensor has demonstrated its effectiveness:

[0045] 1) Medical Scientific and Educational Center of Moscow State University named after M.V. Lomonosov (Lomonosovsky Prospekt, Building 27, Building 10).

[0046] 2) City Clinical Hospital named after D.D. Pletnev (State Budgetary Healthcare Institution "City Clinical Hospital named after D.D. Pletnev of the Health Department of the City of Moscow" 105077, Moscow, 11th Parkovaya St., 32, building 1, building 2, building 3, building 4).

[0047] 3) Institute of Urology and Human Reproductive Health. Urology Clinic named after R.M. Fronshtein (Moscow, B. Pirogovskaya St., 2, building 1).

[0048] Stones on which clinical studies of various types of urological stones from the series were carried out:

[0049] - oxalate,

[0050] - carbonate (carbonapatite),

[0051] - urate

[0052] - cystine,

[0053] - phosphate,

[0054] - struvite and gallstones:

[0055] - cholesterol,

[0056] - pigmented.

[0057] It should be obvious to those skilled in the art that the invention is not limited to the embodiments presented above and that variations may be included within the scope of the claims. The distinctive features presented in the description together with other distinctive features may, if necessary, also be used separately from each other. References. 1. Maksimova T.G., Popova I.N. Econometrics: a teaching aid / T.G.

[0058] Maksimova, I.N. Popova. - SPb.: University ITMO, 2018. - 70 p.

Claims

Invention formula 1. A method for recognizing an object - a stone and / or soft biological tissue - during a laser lithotripsy surgery, consisting of analyzing the light reflected from the object by the source used, characterized in that the reflected light is received by means of a laser fiber aimed at the object in the absence of laser radiation, the levels of light reflected from the object are recorded at least at two wavelengths 1(11) and 12) and their normalized values ​​are calculated in relation to previously measured light levels at the corresponding wavelengths the mentioned source when reflected from the reference body before the operation, as the logarithm of their ratio 1*(Л£) = lg (i(Аi) / ioP.i)), (1) where £=1.2 is the ordinal number of the wavelength then, to separate objects into two classes - stone or soft tissue - an algorithm of data processing of the type (1) is used according to a certain criterion for recognizing a stone in the aperture of a laser fiber, based on a comparison of the weight terms of the algebraic sum of the normalized signals (1): where , c are weighting numerical coefficients If this condition is met, then the fiber is directed towards the soft tissue, if not, towards the stone.

2. The method according to item 1, in which criterion (2) is calculated in the range of wavelengths: 540 - 630 nm 3. The method according to item 2, in which criterion (2) is calculated at two wavelengths: 575±5 and 600±5 nm.

4. The method according to paragraph 3, in which criterion (2) is calculated at three wavelengths: 550±5, 575±5 and 600±5 nm.

5. The method according to claim 1, in which the light source used is a source with a continuous spectrum in the wavelength ranges of criterion (2).

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