Method for acquiring spatio-temporal characteristics of pulmonary ventilation

Abstract

The present application relates to a kind of fusion lung ventilation spatiotemporal feature acquisition method, on the basis of establishing three-dimensional electrical impedance image, carry out the visualization research of lung dynamic ventilation condition, fusion evaluation lung ventilation time and spatial heterogeneity, for dynamic respiratory process, the activity of each three-dimensional electrical impedance image will be obtained in time sequence arrangement and obtain three-dimensional electrical impedance activity curve, extract fusion lung ventilation spatiotemporal feature from three-dimensional electrical impedance activity curve for lung function assessment.Can realize long-term continuous dynamic monitoring;First use three-dimensional EIT to carry out lung function research, can be dynamically observed to whole lung ventilation, fusion evaluation lung ventilation time and spatial heterogeneity, convert into three-dimensional electrical impedance activity curve, it is beneficial to clinical auxiliary diagnosis and local lung function characterization.

Description

Technical Field

[0001] This invention relates to a clinical auxiliary diagnostic technique, and more particularly to a method for obtaining spatiotemporal features of pulmonary ventilation. Background Technology

[0002] Respiratory diseases are a major challenge affecting people's health and quality of life. The lungs are the main organ of the respiratory system, and lung ventilation function is a key focus in clinical practice. Common diagnostic methods for lung diseases include X-rays, MRI, and computed tomography (CT), but these methods can only characterize the structural features of the lungs and cannot reveal functional lesions that precede structural changes; furthermore, these devices emit radiation and are expensive, thus their accessibility is very limited.

[0003] Pulmonary function tests focus on the general characteristics and severity of lung activity, such as lung volume and airway patency. They can clarify the degree and type of respiratory function decline and are a primary means of evaluating disease progression or treatment effectiveness. During pulmonary function testing, subjects typically stand or sit and perform prescribed breathing movements under the guidance of a physician. Using a nose clip and mouthpiece, airflow is completely passed through a spirometer, which provides the volume and rate of air intake and output. This method can only provide a holistic evaluation of the respiratory system and is difficult to characterize localized changes in lung function, such as early airway alterations and localized lung parenchymal damage. This is highly detrimental to the prevention and treatment of chronic respiratory diseases. Bilateral pulmonary function testing can measure the functional changes of one lung separately, but it requires double-lumen endotracheal intubation, which is more invasive and inconvenient, and is rarely used clinically. Summary of the Invention

[0004] To address the issue of accurate lung function testing, a method for acquiring spatiotemporal features of lung ventilation is proposed. By using three-dimensional EIT technology, the dynamic ventilation status of the lungs is visualized, and the temporal and spatial heterogeneity of lung ventilation is evaluated. The results are then converted into a three-dimensional electrical impedance activity curve, which reflects respiratory characteristics and is used to comprehensively assess the lung ventilation status of the subjects.

[0005] The technical solution of the present invention is: a method for obtaining spatiotemporal features of fused lung ventilation, specifically including the following steps:

[0006] 1) Obtaining a three-dimensional electrical impedance image through electrical impedance imaging: Electrical impedance imaging involves acquiring the conductivity values ​​within the imaging area, summing the conductivity values ​​of all pixels at a certain moment to obtain the global conductivity value at that moment, and obtaining the three-dimensional electrical impedance image at that moment. The global conductivity values ​​of the entire breathing process are arranged in chronological order to obtain a time-series three-dimensional electrical impedance image of the breathing process.

[0007] 2) Define active pixels: pixels whose pixel value is in the top x% of the total image area; define activity level: the proportion of active pixels to the total number of pixels in the image area; calculate the activity level of the time series 3D electrical impedance image from step 1);

[0008] 3) For the dynamic breathing process, the activity of each three-dimensional electrical impedance image obtained in step 2) is arranged in chronological order to obtain a three-dimensional electrical impedance activity curve. The spatiotemporal features of fused lung ventilation, including AR, are extracted from the three-dimensional electrical impedance activity curve. max AR sec and S exp ;

[0009] AR max This represents the peak value of the activity curve;

[0010] The peak begins at the start of the expiratory phase. start F start The activity value corresponding to the next second is defined as the activity value AR at one second of exhalation. sec ;

[0011] S exp The area of ​​the shadow under the expiratory phase, starting from the expiratory phase (F). start F at the end of the expiratory phase end The area covered by the activity curve.

[0012] A method for assessing lung ventilation using a three-dimensional electrical impedance activity curve that integrates spatiotemporal characteristics of lung ventilation, wherein the three-dimensional electrical impedance activity curve is used to assess the degree of lung ventilation obstruction; the peak AR value of the activity curve is... max Used to reflect the degree of lung expansion at the end of a forced inspiration; the activity value at one second of expiration is AR. sec and the area of ​​the shadow under the expiratory segment S exp It is used to indicate the degree of tracheal patency or lung obstruction.

[0013] The beneficial effects of this invention are as follows: This invention integrates a method for acquiring spatiotemporal characteristics of lung ventilation, which features high temporal resolution of electrical impedance imaging, compact structure, low cost, safety and no radiation, and low environmental requirements, enabling long-term continuous dynamic monitoring; it is the first to use three-dimensional EIT for lung function research, which can dynamically observe whole-lung ventilation, integrate and evaluate the temporal and spatial heterogeneity of lung ventilation, and convert it into a three-dimensional electrical impedance activity curve, which is beneficial for clinical auxiliary diagnosis and local lung function characterization. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the three-dimensional electrical impedance imaging dynamic process of lung exhalation according to the present invention;

[0015] Figure 2 This is a schematic diagram of the domain of interest division in the three-dimensional imaging region of the present invention;

[0016] Figure 3A This is a comparison chart of the mid-expiratory mean flow rate (MF) values ​​between the normal and abnormal groups according to the present invention.

[0017] Figure 3B This invention provides a subject curve analysis diagram for MF.

[0018] Figure 4 This is a schematic diagram of the statistical parameters of the activity curve of the present invention;

[0019] Figure 5A This is a graph showing the average activity level of each group in this invention.

[0020] Figure 5B AR is the activity value of each group during one second of exhalation in this invention. sec picture;

[0021] Figure 5C The peak AR value of the activity curves for each group in this invention. max picture;

[0022] Figure 5D The expiratory shadow area S of each group in this invention exp picture;

[0023] Figure 6 This is a graph showing the activity of bronchiectasis-positive subjects before and after bronchiectasis in this invention.

[0024] Figure 7 This is a schematic diagram of the activity curves of subjects with different degrees of blockage according to the present invention. Detailed Implementation

[0025] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0026] Electrical impedance tomography (EIT) is a radiation-free, non-invasive, low-cost, and functional imaging technique. The basic principle of EIT can be described as applying a safe current below the cellular excitation threshold to the human body using various excitation methods and electrode arrangements, and then retrieving an image of the body's conductivity distribution or changes based on surface voltage distribution data. EIT can capture changes in electrical impedance within the thoracic cavity during respiration, revealing the spatiotemporal heterogeneity of lung ventilation.

[0027] Electrical impedance imaging (EIT) offers high temporal resolution, a compact structure, low cost, safety with no radiation, and low environmental requirements, enabling long-term continuous dynamic monitoring. Currently, two-dimensional EIT is widely used in clinical research, but its assessment of lung ventilation is not comprehensive.

[0028] Using three-dimensional EIT for lung function studies allows for dynamic monitoring of whole-lung ventilation. For example... Figure 1 The diagram shows a schematic representation of the dynamic process of lung exhalation reconstructed using three-dimensional electrical impedance tomography. As exhalation proceeds, the pulmonary conductivity gradually decreases, indicating that the lungs are gradually emptying and the air content is decreasing.

[0029] As can be seen, pulmonary ventilation is a process with both spatiotemporal heterogeneity: it varies considerably over time and is unevenly distributed spatially. EIT reconstruction yields the conductivity values ​​within the imaging region. Summing the conductivity values ​​of all pixels at a given moment provides the global conductivity value for that moment. Arranging the global conductivity values ​​of a given respiratory process in chronological order yields the EIT global conductivity curve.

[0030] To evaluate the spatial heterogeneity of lung ventilation, the imaging region was divided into eight sub-regions according to spatial distribution, each serving as a region of interest, such as... Figure 2 The diagram shows the division of the interest region in the three-dimensional imaging area. The imaging area is divided into 8 sub-regions in space by three mutually perpendicular surfaces.

[0031] Based on the global conductivity curve of EIT, a mid-expiratory mean flow rate (MF, the average flow rate of 25%–75% of forced expiratory vital capacity) is proposed to describe the smoothness of ventilation, reflecting the temporal heterogeneity of pulmonary ventilation to some extent. Similarly, by limiting the study pixels to all pixels of a certain sub-region, the local conductivity curve of that sub-region can be obtained. Likewise, the rMF of a certain region can reflect the ventilation smoothness of that region. The local MF value of the i-th sub-region is denoted as rMF. i For a given ventilation process, rMF 1-8 The coefficient of variation can, to some extent, reflect the spatiotemporal heterogeneity of ventilation.

[0032] Based on the obtained 3D EIT image information, the study included 137 participants, who were divided into normal and abnormal groups according to their lung function test results. The study addressed the eight sub-regions defined above, such as... Figure 3A As shown, a significant difference in MF values ​​was observed between the normal and abnormal groups (statistical difference P < 0.01). Furthermore, as... Figure 3BAs shown, receiver operating characteristic (ROC) analysis was performed on MF (Receptor Characteristic Curve). ROC obtains multiple pairs of sensitivity and specificity by shifting the cutoff point / cutoff value. A curve is plotted with sensitivity on the ordinate and false positive rate on the abscissa, and the area under the curve is calculated; the larger the area, the higher the diagnostic value. Clinical statistics showed that 17.24 was the diagnostic cutoff value. MF's sensitivity (the probability of correctly identifying a true value as true) for abnormal ventilation was 74%, its specificity (the probability of correctly identifying a false value as false) was 69%, and its area under the curve (AUC) for predictive validity was 0.747 (95% CI 0.665–0.829; P = 0.001). However, compared to the classic two-dimensional EIT parameter, the global inhomogeneity (GI), the AUC for predicting abnormal ventilation was 0.535. Therefore, MF demonstrates unprecedented superiority, and the above theory has been well validated by experimental data.

[0033] Combining MF characteristic curve ROC analysis and 3D EIT image information, the proportion of the actively ventilated region in the overall imaging area varies at different times, reflecting the spatial variation of gas distribution. Therefore, for a given 3D EIT image, we designed the activity index to fuse spatiotemporal heterogeneity. First, several definitions need to be clarified:

[0034] Active pixels: Pixels whose pixel value is in the top x percent, where x is an empirical value, here taken as 80.

[0035] Activity level: The proportion of active pixels in the total imaging area.

[0036] For the dynamic breathing process, the activity level of each image is arranged in chronological order to obtain an activity curve, such as... Figure 4 As shown, AR max This represents the peak of the activity curve, which begins at the start of the expiratory phase (F). start F start The activity value corresponding to the next second is defined as the activity value at one second of exhalation (AR). sec Starting from the exhalation phase, F start F at the end of the expiratory phase end The area enclosed by the activity curve is the shaded area S under the expiratory phase. exp .

[0037] The activity curve can reflect some characteristics of breathing. Specifically, the peak AR of the activity curve... max It can reflect, to some extent, the degree of lung expansion at the end of a forceful inhalation. The activity value (AR) at one second of exhalation... sec and the area of ​​the shadow under the expiratory segment Sexp It can reflect the smoothness of exhalation. We divided 137 subjects into four groups according to their pulmonary function test results: Normal, Restricted, Obstructive, and Mixed. The activity levels of each group are as follows: Figures 5A-5D As shown. It can be seen that the AR of the restriction group Obstruct... max A lower value indicates poor lung expansion; AR value of the restricted group and the mixed group at one second of expiration. sec and the area of ​​the shadow under the expiratory segment S exp A higher reading indicates impaired exhalation, consistent with theoretical expectations and MF analysis results. Based on comprehensive clinical data, this method can effectively identify abnormal ventilation conditions.

[0038] To minimize the impact of individual differences among subjects, we compared the results of a subject with a positive bronchodilator test. Figure 6 As shown, before and after bronchiectasis, AR max Similar values ​​indicate little difference in the degree of lung expansion at the end of inspiration. After bronchodilation, tracheal patency increases, and AR... sec and S exp The decrease was significant and consistent with physiological expectations.

[0039] Furthermore, we preliminarily verified the feasibility of using activity curves to assess the degree of obstruction. We selected four participants, numbered 1-2-3-4, corresponding to pulmonary function conclusions of mild obstruction, moderate to severe obstruction, severe obstruction, and very severe obstruction, respectively. Figure 7 As shown, the corresponding AR activity curve of the participants can be seen. sec and S exp Increasing.

[0040] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for acquiring spatiotemporal features of fused lung ventilation, characterized in that, Specifically, the steps include the following: 1) Obtaining a three-dimensional electrical impedance image through electrical impedance imaging: Electrical impedance imaging involves acquiring the conductivity values ​​within the imaging area, summing the conductivity values ​​of all pixels at a certain moment to obtain the global conductivity value at that moment, and obtaining the three-dimensional electrical impedance image at that moment. The global conductivity values ​​of the entire breathing process are arranged in chronological order to obtain a time-series three-dimensional electrical impedance image of the breathing process. 2) Define active pixels: pixels whose pixel value is in the top x% of the total image area; define activity level: the proportion of active pixels to the total number of pixels in the image area; calculate the activity level of the time series 3D electrical impedance image from step 1); 3) For the dynamic breathing process, the activity of each three-dimensional electrical impedance image obtained in step 2) is arranged in chronological order to obtain a three-dimensional electrical impedance activity curve. The spatiotemporal features of fused lung ventilation, including AR, are extracted from the three-dimensional electrical impedance activity curve. max AR sec and S exp ; AR max This represents the peak value of the activity curve; The peak begins at the start of the expiratory phase. start F start The activity value corresponding to the next second is defined as the activity value AR at one second of exhalation. sec ; S exp The area of ​​the shadow under the expiratory phase, starting from the expiratory phase (F). start F at the end of the expiratory phase end The area covered by the activity curve.

2. A method for assessing lung ventilation using a three-dimensional electrical impedance activity curve that integrates the spatiotemporal characteristics of lung ventilation, characterized in that, The three-dimensional electrical impedance activity curve is used to assess the degree of pulmonary ventilation obstruction: the peak AR value of the activity curve... max Used to reflect the degree of lung expansion at the end of a forced inspiration; the activity value at one second of expiration is AR. sec and the area of ​​the shadow under the expiratory segment S exp It is used to indicate the degree of tracheal patency or lung obstruction.

Images