A method for establishing a photoacoustic imaging model for monitoring acid-base imbalance

Abstract

The present invention discloses a method for establishing a photoacoustic imaging model for monitoring acid-base imbalance, which belongs to the field of acid-base imbalance detection and includes the following steps: S1: establishing a lactic acidosis model in an experimental animal; the lactic acidosis model includes: infusing the experimental animal in the perioperative period with a lactic acid solution of different concentrations; S2: performing a blood gas analysis on the experimental animal in the lactic acidosis model; wherein, after the lactic acid solution is pumped intravenously, the experimental animal is subjected to an arterial puncture and a blood gas analysis is performed to measure the acid-base abnormality of the experimental animal; S3: using a photoacoustic microscope to monitor the intracranial blood vessels of the experimental animal; S4: filtering and binarizing the photoacoustic image, and automatically performing quantitative analysis on the blood vessel diameter, blood vessel length, and blood vessel density, monitoring the dynamic changes in pH, and obtaining the relationship between the changes in intracranial blood vessel diameter and pH. The present invention can achieve non-invasive, in vivo, real-time monitoring of acidosis, alkalosis, and brain function metabolism.

Description

Technical Field

[0001] The present invention relates to the technical field of acid-base imbalance detection, and in particular to a method for establishing a photoacoustic imaging model for monitoring acid-base imbalance. Background Art

[0002] Surgical stress is associated with a significant risk of systemic complications as it may include a wide range of endocrine, hematological, and immunological effects. Careful perioperative management and monitoring during anesthesia are essential. It is well known that elevated blood lactate is one of the predictors of poor prognosis. Hyperlactatemia is often associated with inadequate tissue perfusion. However, other studies have shown that in patients with sepsis and septic shock, increasing systemic or regional oxygen supply does not prevent the increase in blood lactate concentration caused by mitochondrial dysfunction. Patients with chronic diseases (such as diabetes and chronic renal failure) are at increased risk of acid-base abnormalities during surgery.

[0003] In the intensive care unit, lactic acidosis is a common cause of acidemia, often accompanied by hemodynamic or respiratory compromise. Arterial puncture is routinely performed for blood gas analysis. However, technical difficulties are frequently reported, significantly increasing the medical workload. Prolonged and repeated punctures may compromise radial artery patency. In critically ill patients with difficult punctures, the lag in technical issues often delays optimal treatment, a significant risk for the patient.

[0004] In summary, existing methods for monitoring the dynamic changes of pH in vivo have the following disadvantages:

[0005] 1. Currently, arterial blood gas puncture is difficult, and repeated punctures over a long period of time may affect the patency of the radial artery. For critically ill patients with difficult punctures, the lag in technical issues often delays the optimal treatment time.

[0006] 2. Arterial blood gas analysis is difficult, costly, and time-consuming.

[0007] Therefore, there is an urgent need to develop a real-time non-invasive method to monitor the dynamic changes of pH in the body to quantitatively evaluate the acid-base balance homeostasis in critically ill patients during the perioperative period.

[0008] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the Invention

[0009] The purpose of the present invention is to provide a method for establishing a photoacoustic imaging model for monitoring acid-base imbalance, and to propose a non-invasive, real-time monitoring of acidosis, alkalosis, and brain functional metabolism based on molecular imaging methods, thereby improving existing detection sensitivity and reducing detection costs and time.

[0010] To achieve the above objectives, the present invention provides a method for establishing a photoacoustic imaging model for monitoring acid-base imbalance, comprising:

[0011] S1: establishing a lactic acidosis model in experimental animals; the lactic acidosis model comprises: infusing lactic acid solutions of different concentrations into the experimental animals during the perioperative period;

[0012] S2: Perform blood gas analysis on experimental animals in a lactic acidosis model; after intravenous pumping of lactic acid solution, the experimental animals are subjected to arterial puncture and blood gas analysis is performed to measure the acid-base abnormalities of the experimental animals;

[0013] S3: Monitoring intracranial vasculature in experimental animals using photoacoustic microscopy; comprehensive and quantitative characterization of mouse vasculature during perioperative care, generating photoacoustic images of the brain vasculature;

[0014] S4: Filter and binarize the photoacoustic image, and automatically perform quantitative analysis on the vascular diameter, vascular length, and vascular density to monitor the dynamic changes in pH and obtain the relationship between changes in intracranial vascular diameter and pH.

[0015] In one embodiment of the present invention, step S1 includes:

[0016] S101: dissolving L-(+)-lactic acid in physiological saline to obtain solutions with lactic acid concentrations of 1%, 3%, 4% and 5%, respectively;

[0017] S102: An indwelling needle was implanted into the tail vein of the experimental animal, and the peritoneum of the experimental animal was treated with 20% urethane solution to simulate the anesthesia state during surgery, and perioperative care was performed; lactate infusion was performed during the perioperative care to establish a perioperative metabolic acidosis model with different pH values, and the electrocardiogram and oxygen saturation were monitored.

[0018] In one embodiment of the present invention, step S2 includes: drawing fresh arterial blood for arterial blood gas analysis; the time for drawing fresh arterial blood is selected as four time points: before lactic acid injection, 30 minutes, 60 minutes and 90 minutes after lactic acid injection.

[0019] In one embodiment of the present invention, in step S3, surgery is required to be performed on the experimental animal to monitor the intracranial blood vessels of the experimental animal using a photoacoustic microscope. The surgery is: placing the anesthetized experimental animal on a headrest platform and opening its scalp with scissors to expose the skull.

[0020] In one embodiment of the present invention, in step S3, the specific process of comprehensively and quantitatively characterizing the blood vessels of the experimental animal is as follows: the scanning area is placed on the head of the experimental animal below the PAM system, and the brain vascular system of the experimental animal is imaged using lasers with wavelengths of 532 nm and 559 nm.

[0021] In one embodiment of the present invention, in step S4, Gaussian filtering is used to enhance the two-dimensional blood vessels with linear structures, and a threshold method is used to separate the signal from the background.

[0022] In one embodiment of the present invention, in step S4, the blood vessel length is calculated as follows: a skeleton is obtained through the blood vessel edge and the skeleton length is calculated; 8 adjacent pixel fields are used as targets at each point of the blood vessel skeleton to calculate the length, and the length divided by 2 is the blood vessel length.

[0023] In one embodiment of the present invention, in step S4, the blood vessel density is calculated as follows: dividing the signal pixels by the total pixels in the binary image to calculate the blood vessel length.

[0024] Compared with the prior art, the method for establishing a photoacoustic imaging model for monitoring acid-base imbalance according to the present invention has the following advantages:

[0025] 1. Predict in vivo pH through real-time non-invasive methods to improve detection specificity and sensitivity.

[0026] 2. Continuously monitor the metabolic microenvironment of the central nervous system during the perioperative period, while assisting with the use of functional imaging and algorithmic analysis techniques to provide a theoretical basis for the clinical treatment of systemic acid-base imbalance, perioperative brain protection, and further development of real-time acid-base balance detection methods during clinical surgery. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The present invention is a flowchart of a method for establishing a photoacoustic imaging model for monitoring acid-base imbalance according to one embodiment of the present invention.

[0028] Figure 2 Schematic diagram of real-time monitoring of dynamic changes in intracranial vascular structure and function before and after lactic acidosis using a photoacoustic microscope according to one embodiment of the present invention.

[0029] Figure 3 FIG. 4 is a schematic diagram showing the blood vessel length according to quantitative photoacoustic imaging results according to one embodiment of the present invention.

[0030] Figure 4 FIG. 4 is a schematic diagram showing the dynamic change of diameter according to the quantitative photoacoustic imaging result of one embodiment of the present invention.

[0031] Figure 5 Schematic diagram of the relationship between pH change rate and diameter change rate according to one embodiment of the present invention. DETAILED DESCRIPTION

[0032] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0033] Unless expressly stated otherwise, throughout the specification and claims, the term "comprise" or variations such as "include" or "comprising", etc., will be understood to include the stated elements or components but not to exclude other elements or other components.

[0034] like Figures 1 to 3 As shown, a method for establishing a photoacoustic imaging model for monitoring acid-base imbalance according to a preferred embodiment of the present invention includes the following steps:

[0035] S1: Establishing a lactic acidosis model in experimental animals. This specifically includes: infusing lactic acid solutions of varying concentrations into the experimental animals during the perioperative period. The experimental animals are preferably mice.

[0036] This step S1 specifically includes the following steps:

[0037] S101: L-(+)-lactic acid is dissolved in physiological saline and diluted to solutions with mass fractions of 1%, 3%, 4% and 5%.

[0038] S102: An indwelling catheter was implanted into the tail vein of the experimental animal, and the animal was treated intraperitoneally with 20% urethane solution (0.5 mg / g) to simulate anesthesia during surgery. Perioperative care was then provided. During perioperative care, lactate was infused to establish a perioperative metabolic acidosis model with varying pH values, and electrocardiogram (ECG) and oxygen saturation were monitored using an electrocardiogram monitor.

[0039] Specifically, 20 experimental animals were randomly divided into four equal groups (n = 4 animals per group). Lactic acid solutions of 1%, 3%, 4%, and 5% concentrations were intravenously pumped into the experimental animals to produce varying degrees of acidosis. A control group received normal saline. During the injection, an indwelling needle was connected to the prepared lactic acid solution and the solution was injected into the experimental animals at a constant rate (5 μL / s). The injection dose for each experimental animal was 12 ml / kg.

[0040] Among them, perioperative care included placing a heating pad under the animal to maintain body temperature close to 37°C.

[0041] S2: Performing blood gas analysis on the experimental animals in the lactic acidosis model, wherein after the lactic acid solution is pumped intravenously for a certain period of time (preferably 5 minutes), the experimental animals are subjected to arterial puncture and blood gas analysis is performed to measure the acid-base abnormality of the experimental animals.

[0042] Specifically, after anesthetizing the experimental animals with an intraperitoneal injection of 20% urethane solution, the injection site on the skin along the midline of the neck was disinfected. The skin was then opened and a 2-cm top-down incision was made. The vessels were isolated to expose the common carotid artery, the distal end was connected with silk suture, and the artery was occluded using a vascular clamp. Afterwards, a micro-PE10 catheter with a fixed silk knot was inserted, and the arterial clamp was immediately released. 0.3 mL of fresh arterial blood was drawn using a heparinized vacutainer connected to a 1 mL syringe. Fresh arterial blood was drawn at four time points: before lactate injection and 30, 60, and 90 minutes after lactate injection.

[0043] Arterial blood gas analysis was performed on freshly drawn arterial blood using an ABL800 blood gas analyzer to assess pH, partial pressure of oxygen (PaO2), partial pressure of carbon dioxide (PaCO2), bicarbonate concentration, base excess (BE), HCO3-, Lac, and sO2.

[0044] S3: Monitor the intracranial vasculature of experimental animals using photoacoustic microscopy. Specifically, a photoacoustic microscopy system with a spatial resolution of 5 μm was used to comprehensively and quantitatively characterize the blood vessels of perioperative experimental animals, generating photoacoustic images. A commercial G2 OR-PAM (manufactured by INNO LASER) was used as the photoacoustic microscopy system.

[0045] Figure 2 Figure 2 shows the real-time monitoring of dynamic changes in intracranial vascular structure and function before and after lactic acidosis using photoacoustic microscopy.

[0046] In step S3, surgery needs to be performed on the experimental animal to monitor the intracranial blood vessels of the experimental animal using a photoacoustic microscope. The surgical procedure is: placing the anesthetized experimental animal on a headrest platform, and opening its scalp with scissors to expose the skull.

[0047] The detailed process for comprehensive and quantitative characterization of the animal's blood vessels is as follows: The scanning area is placed on the animal's head under a photoacoustic microscope, and the animal's brain vasculature is imaged using lasers with wavelengths of 532 nm and 559 nm. The acoustic signal generated by the laser irradiation on the imaging tissue is amplified by a 50 dB amplifier and received by a 50 MHz ultrasonic transducer.

[0048] The acidosis state of the animals was simulated by injecting different concentrations of lactic acid in step S1, and photoacoustic images were taken 2 minutes before and 2 minutes after the injection.

[0049] S4: Extraction of vascular structure and function information. After filtering and binarization of the photoacoustic images, automatic quantitative analysis of vascular diameter, length, and density is performed. Dynamic changes in pH are monitored to determine the relationship between changes in intracranial vascular diameter and pH.

[0050] Specifically, MATLAB R2021b (MathWorks, Natick, USA) was used to process the photoacoustic images. After image filtering and binarization, the vessel diameter, vessel length, and vessel density were automatically quantitatively analyzed. Gaussian filtering was used to enhance the two-dimensional (2D) vessels with linear structures. By setting an initial threshold, signals greater than the threshold were identified as vessel signals, and signals less than the threshold were identified as background signals. The two signals were set to 1 and 0, respectively, and the threshold value was continuously adjusted so that the observed separation results could separate the vascular area as completely as possible. The purpose was to separate the vessels as much as possible from the perspective of naked eye observation. Figure 3 and 4 The quantitative photoacoustic imaging results are shown in the figure, which show the dynamic changes in blood vessel length and diameter. Among them, the quantitative results show that the total length of the cortical blood vessels of the experimental animals decreased, while the total diameter increased.

[0051] The vascular skeleton extraction function provided in MATLAB was used to extract the skeleton of the vascular region. The lengths of the skeletons were then summed to obtain the final total vessel length. At each point in the vascular skeleton, the length was calculated using eight adjacent pixel fields as targets. This length, divided by two, was considered the actual vessel length. Vessel density was calculated by dividing the signal pixels by the total number of pixels in the binary image.

[0052] In addition, step S4 also includes manually measuring the diameter of blood vessels in the region of interest. Specifically, the cerebral cortex is divided into four quadrants (upper left, lower left, upper right, and lower right), and three blood vessels with clear images and a diameter less than 40 μm are randomly selected in each quadrant by visual observation.

[0053] Data were extracted from the selected blood vessels in the photoacoustic image and processed using Origin Pro software. Specifically, a Gaussian function was used to fit and calculate its full width at half maximum (FWHM), which was defined as the diameter of the blood vessel.

[0054] Figure 5 The figure shows that the diameter quantitative information is displayed in real time: the diameter change responds to the pH change in real time. In the figure, 1%, 3%, 4% and 5% lactic acid concentrations correspond to pH change rates of 10%, 20%, 30% and 40%, respectively. The change in intracranial blood vessel diameter is positively correlated with pH.

[0055] In addition, the oxygen saturation of hemoglobin is related to the concentrations of HbR and HbO2. The concentrations of HbR and HbO2 can be quantified based on the principle of spectral decomposition. By imaging the two proteins, the oxygen saturation can be obtained from the perspective of image analysis. Specifically, the intensity of the photoacoustic signal at a certain wavelength is the result of the linear superposition of the two hemoglobins and the corresponding molar absorption coefficients. By analyzing the photoacoustic images obtained by scanning the two wavelengths, the concentration ratio of the two substances can be separated. Furthermore, the oxygen saturation of hemoglobin can be obtained from the concentrations of HbR and HbO2, and then the level of brain functional metabolism can be obtained.

[0056] The utility of vessel diameter in monitoring perioperative pH was evaluated using R statistical software, version 4.2.0 (R Statistical Computing Project). Differences in numerical variables between groups were detected using the Kruskal-Wallis test (P < 0.01). Diagnostic performance was determined by plotting the area under the curve (AUC) using the true-positive rate on the y-axis and the false-positive rate on the abscissa, based on a binary classification approach.

[0057] The optimal threshold for the rate of change in vessel diameter for diagnosing clinically significant mild, moderate, and severe metabolic acidosis was determined by combining sensitivity and specificity information from the Youden index. A two-tailed P value of less than 0.05 was considered significant. Dynamic changes in pH are predicted and reflected by structural and functional information.

[0058] In this method, lactate is continuously pumped into the tail vein of experimental animals to simulate perioperative acidosis caused by elevated lactate. The animals are then anesthetized, their scalps are incised, and the skulls are exposed. The scanning area is placed under the PAM system, and the animal's cerebral vasculature is imaged using lasers at wavelengths of 532nm and 559nm, enabling dynamic monitoring of the animal's intracranial blood vessels.

[0059] Because intracranial blood vessels are extremely sensitive to the pH of the internal environment, an algorithm was used to extract their vascular characteristics and automatically quantify their diameter, length, and density. Correlations between the blood gas analysis results of the experimental animals and the density, length, and diameter were then analyzed. Dynamic changes in pH were predicted and reflected through structural and functional information.

[0060] The method for establishing a photoacoustic imaging model for monitoring acid-base imbalance of the present invention can provide a theoretical basis for the clinical treatment of systemic acid-base imbalance, perioperative brain protection, and further development of real-time acid-base balance detection methods during clinical surgery, and continuously monitor the metabolic microenvironment of the central nervous system during the perioperative period.

[0061] The foregoing descriptions of specific exemplary embodiments of the present invention are for purposes of illustration and description. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is apparent that many variations and modifications are possible in light of the foregoing teachings. The exemplary embodiments have been selected and described for the purpose of explaining the specific principles of the invention and their practical application, thereby enabling those skilled in the art to realize and utilize a variety of exemplary embodiments of the invention and various options and modifications. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for establishing a photoacoustic imaging model for monitoring acid-base imbalance, characterized in that: include: S1: Establishment of lactic acidosis model in experimental animals; The lactic acidosis model comprises: infusing lactic acid solutions of different concentrations into experimental animals during the perioperative period; S2: Perform blood gas analysis on experimental animals in a lactic acidosis model; after intravenous pumping of lactic acid solution, the experimental animals are subjected to arterial puncture and blood gas analysis is performed to measure the acid-base abnormalities of the experimental animals; S3: Monitoring intracranial vasculature in experimental animals using photoacoustic microscopy; comprehensive and quantitative characterization of intracranial vasculature in experimental animals during perioperative care, generating photoacoustic images of the brain vasculature; S4: filtering and binarizing the photoacoustic image, and automatically quantitatively analyzing the diameter, length, and density of blood vessels within the skull of the experimental animal; performing arterial puncture on the intracranial blood vessels of the experimental animal and performing blood gas analysis to monitor dynamic changes in pH, obtaining a positive correlation between changes in the diameter of blood vessels within the skull of the experimental animal and changes in pH; and a p-value of a Kruskal-Worthley test after statistical calculation of the relationship between changes in the diameter of blood vessels within the skull of the experimental animal and changes in pH being less than 0.001; wherein a Gaussian function is used to fit the selected blood vessels in the photoacoustic image and calculate the half-maximum width of the selected blood vessels, which is the blood vessel diameter; The step S1 comprises: S101: dissolving L-(+)-lactic acid in physiological saline to obtain solutions with lactic acid concentrations of 1%, 3%, 4%, and 5%, respectively; wherein the lactic acid concentrations of 1%, 3%, 4%, and 5% correspond to pH change rates of 10%, 20%, 30%, and 40%, respectively; S102: An indwelling needle was implanted into the tail vein of the experimental animal, and the peritoneum of the experimental animal was treated with 20% urethane solution to simulate the anesthesia state during surgery, and perioperative care was performed; lactate infusion was performed during the perioperative care to establish a perioperative metabolic acidosis model with different pH values, and the electrocardiogram and oxygen saturation were monitored.

2. The method for establishing a photoacoustic imaging model for monitoring acid-base imbalance according to claim 1, wherein: The step S2 includes: drawing fresh arterial blood for arterial blood gas analysis; the time for drawing fresh arterial blood is selected as four time points: before lactic acid injection, 30 minutes, 60 minutes and 90 minutes after lactic acid injection.

3. The method for establishing a photoacoustic imaging model for monitoring acid-base imbalance according to claim 1, wherein: In step S3, an operation is required to be performed on the experimental animal to monitor the intracranial blood vessels of the experimental animal using a photoacoustic microscope. The operation is as follows: placing the anesthetized experimental animal on a headrest platform, and opening its scalp with scissors to expose the skull.

4. The method for establishing a photoacoustic imaging model for monitoring acid-base imbalance according to claim 1, wherein: In step S3, the specific process of the step of comprehensively and quantitatively characterizing the blood vessels of the experimental animal during perioperative care is as follows: the scanning area is placed on the head of the experimental animal under the PAM system, and the brain vascular system of the experimental animal is imaged by lasers with wavelengths of 532nm and 559nm.

5. The method for establishing a photoacoustic imaging model for monitoring acid-base imbalance according to claim 1, wherein: In step S4, Gaussian filtering is used to enhance the two-dimensional blood vessels with linear structures, and a threshold method is used to separate the signal from the background.

6. The method for establishing a photoacoustic imaging model for monitoring acid-base imbalance according to claim 5, wherein: In step S4, the blood vessel length is calculated as follows: a skeleton is obtained through the blood vessel edge, and the skeleton length is calculated; 8 adjacent pixel fields are used as targets at each point of the skeleton to calculate a first length; the first length is divided by 2 to obtain the blood vessel length.

7. The method for establishing a photoacoustic imaging model for monitoring acid-base imbalance according to claim 5, wherein: In step S4, the blood vessel density is calculated as follows: the signal pixel is divided by the total pixel in the binary image to calculate the blood vessel density.

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