CN111449657A - Bedside pulmonary ventilation-blood flow perfusion electrical impedance tomography method based on saline angiography - Google Patents

Abstract

The invention discloses a bedside lung ventilation-blood flow perfusion electrical impedance tomography imaging method based on saline contrast. In addition, the present invention also discloses an image monitoring device, an image monitoring system and a pulmonary embolism diagnosis system based on the above method. The method of the invention improves the imaging quality of blood perfusion, and calculates the dead space ventilation %, the intrapulmonary shunt %, and the regional ventilation-blood flow matching %, which is more practical. The method of the present invention can diagnose pulmonary embolism with a sensitivity of 90.9% and a specificity of 98.6%, and has high clinical application value.

Description

A point-of-care saline-based pulmonary ventilation-perfusion electrical impedance tomography method

technical field

The invention belongs to the field of clinical medicine, and in particular relates to a bedside lung ventilation-blood flow perfusion electrical impedance tomography imaging method based on saline angiography.

Background technique

Electrical impedance tomography (EIT) is a non-invasive imaging technique used to study and detect regional lung ventilation and perfusion (blood flow) in humans and animals. Contrary to conventional methods, EIT does not require the patient to breathe through a tube or sensor, does not apply ionizing X-rays, and can be used for extended periods of time, such as 24 hours or even longer. Therefore, EIT can be used continuously and is therefore suitable for real-time and long-term monitoring of treatment effects. EIT was first used to monitor respiratory function in 1983 and remains the only bedside method that allows continuous, non-invasive detection of regional changes in lung volumes, blood flow, and cardiac activity. More details of this technique can be found in "Electrical impedance tomography" by Costa E.L., Lima R.G., and Amato M.B. in Curr Opin Crit Care, Feb. 2009, 15(1), p.18-24.

In EIT, as disclosed in US Pat. No. 5,626,146, a plurality of electrodes, typically from 8 to 32, are placed on the surface of the body to be examined. The control unit ensures that electrical signals, such as current, are applied to one or more pairs of electrodes on the skin to form an electric field, which in turn is detected by the other electrodes. The electrodes used to apply the current are called "current injection electrodes", although one of them may serve as a reference potential, such as ground. Typically, 3 to 10 mARMS is injected in the frequency range of 0.1-1000kHz. Using the remaining electrodes, the resulting voltage is detected (forming an "EIT data vector" or "scan frame") and subsequently used to estimate the distribution of electrical impedance in the body. Specific algorithms are developed to convert a set of voltages into an image.

At present, bedside pulmonary vascular perfusion imaging based on electrical impedance technology (EIT) is of poor quality and is interfered by electrical resistance signals such as heart beating and pulmonary vascular beating, so it has poor clinical applicability. In order to improve the imaging quality, some studies have developed a saline angiography electrical impedance imaging technique. Saline is injected through a central venous catheter, while apnea is stopped, the changes in the thoracic resistance signal are collected, and the local resistance-time curve of saline angiography is established, but the resistance- There are many types of time curve analysis methods. In the process of saline injection, it is difficult to identify the arrival of saline to the right atrium to reduce the interference of resistance signals and affect imaging analysis. It is a difficult problem to obtain the accurate lung time point when saline first arrives. , the inconsistency of the time of the decrease in the resistance of the lung area and the decrease of the cardiac resistance in a certain area, but the practicability is poor and time-consuming.

For bedside pulmonary blood perfusion imaging analysis, the current electrical impedance technology mostly focuses on the distribution percentage of ventilation and blood flow, which belongs to semi-quantitative evaluation, and it is technically difficult to go deep into the quantitative calculation of ventilation dead space and intrapulmonary shunt.

The purpose of this application is to solve the technical problems of bedside electrical impedance pulmonary blood perfusion imaging, and to improve the accuracy and application value.

SUMMARY OF THE INVENTION

technical problem

One of the objectives of the present invention is to provide a bedside pulmonary ventilation-perfusion electrical impedance tomography imaging method based on saline contrast.

Another object of the present invention is to provide an image monitoring device.

The third object of the present invention is to provide an image monitoring system.

The fourth object of the present invention is to provide a diagnostic method and a diagnostic system for pulmonary embolism.

Technical solutions

According to one aspect of the present invention, the present invention provides a bedside-based saline contrast pulmonary ventilation-perfusion electrical impedance tomography method. The method includes the following steps:

(1) Breath-hold test, which requires at least 8 seconds;

(2) Pulmonary blood perfusion angiography was performed by injecting saline, and the changes of the electrical impedance signal of the chest were continuously collected;

(3) Offline analysis of resistance signal data.

The specific operations of step (1) are as follows: the breath-hold test requires at least 8 seconds (when the ventilator is mechanically ventilated, press the exhale or inspiratory breath-hold button for 10s; spontaneously breathing patients are asked to hold their breath for 8 seconds); after the breath-hold test is passed, Before performing saline angiography EIT examination.

The concentration of the injection saline of the present invention is 10%, and the injection volume is 10ml.

The specific operation of step (2) is as follows: the subject is connected to the pulmonary electrical impedance monitoring instrument, prepare 10% NaCl 10ml, and confirm that the subject has established a central venous catheter; after the breath-holding starts, inject 10% NaCl 10ml into the body from the central venous catheter Pulmonary perfusion angiography was performed; changes in electrical impedance signals of the chest were continuously collected starting 2 minutes before saline injection.

The off-line analysis of the resistance signal data in step (3) includes:

a. Construct pulmonary blood perfusion image;

b. Construct lung ventilation images;

c. Construct lung ventilation/blood flow distribution images.

The specific operation of constructing a pulmonary blood perfusion image in step a is as follows: the overall resistance curve begins to drop during breath-holding as the starting point for saline to enter the body (T0), and after one cardiac cycle as the starting point for saline to enter the pulmonary blood vessels (T1), the lowest overall resistance point as the end point of saline passing through the pulmonary vessels (T2). The resistance curve of the T0-T1 time period reflects the saline entering the right heart and does not reflect the pulmonary vascular perfusion. To reduce interference, the curve of this period is not used in the analysis; T1-T2 is used. A resistance-time curve (slope fit) of each lung region over time periods was constructed.

The specific operation of constructing the lung ventilation image in step b is as follows: the lung ventilation image is constructed by the lung resistance changes of at least 5 consecutive breathing cycles within 1 minute before the injection.

The specific operations for constructing the lung ventilation/blood flow distribution image in step c are as follows: the lung ventilation image and the pulmonary blood flow perfusion image use 20% of the maximum pixel points as a threshold to construct the lung ventilation/blood flow distribution image.

According to another aspect of the present invention, the present invention provides an image monitoring apparatus including a data receiver, an image processor and a controller.

The data receiver is responsible for receiving lung ventilation impedance data and lung blood perfusion impedance data determined based on the lung electrical impedance monitoring instrument.

The image processor is responsible for generating a lung ventilation image and a lung blood perfusion image from the lung ventilation impedance data and the lung blood perfusion impedance data. The image processor generates an image from the impedance data according to the method previously described.

The controller is responsible for controlling and displaying at least one of a lung ventilation image and a lung blood perfusion image according to the screen mode and the measurement site.

The controller may include an image and waveform output control module, an impedance measurement control module, and an information determination and transmission module.

The image and waveform output control module may be configured to control to display at least one of a lung ventilation image, a lung blood perfusion impedance image, and a lung ventilation/blood flow distribution image according to a preset screen mode or a measurement site of an object to be monitored.

The measurement site may refer to a site that is more accurately monitored with respect to the state of at least one of the subject's lungs and heart.

The screen mode may include a plurality of screen areas divided based on a certain pathological state of the subject to display at least one of a lung ventilation image, a lung blood perfusion impedance image, and a lung ventilation/blood flow distribution image.

The impedance measurement control module may be configured to control the electrical impedance monitoring instrument to measure lung ventilation impedance data and pulmonary blood flow perfusion impedance data at the chest of the subject.

The information determination and transmission module may be configured to control the features implemented by the data receiver and the image processor, and to transmit the received lung ventilation impedance data, pulmonary blood flow perfusion impedance data, to the image processor such that the lung ventilation impedance The data, pulmonary perfusion impedance data, can be generated as an image.

Also, the information determination and transmission module may be configured to control transmission of at least one of the received lung ventilation impedance data, pulmonary blood perfusion impedance data, and the generated lung ventilation impedance image, pulmonary blood perfusion impedance image to the outside.

According to yet another aspect of the present invention, the present invention provides an image monitoring system, which includes the aforementioned image monitoring device.

Further, the system may also include a lung electrical impedance monitoring instrument. The lung electrical impedance monitoring instrument is responsible for measuring lung ventilation impedance data and lung blood perfusion impedance data.

According to yet another aspect of the present invention, the present invention provides a method for diagnosing pulmonary embolism, the method comprising constructing an image of pulmonary ventilation/blood flow distribution using the aforementioned method, calculating % dead space ventilation (only ventilation but no blood flow) Perfusion of the area in the percentage of the total area), when the dead space ventilation%> 30.37% diagnosed as pulmonary embolism.

According to yet another aspect of the present invention, the present invention provides a pulmonary embolism diagnosis system, the diagnosis system comprising a diagnosis apparatus, and the diagnosis apparatus operates the aforementioned diagnosis method.

Preferably, the system further comprises the aforementioned image monitoring device.

More preferably, the system further includes a lung electrical impedance monitoring instrument.

Pulmonary embolism refers to a clinical and pathophysiological syndrome in which various emboli enter the pulmonary circulation and block the pulmonary artery or other branches and cause pulmonary circulation disorders. It includes pulmonary thromboembolism, fat embolism syndrome, amniotic fluid embolism, and air embolism.

technical effect

In the method of the present invention, ventilation removes the resistance signal of one cardiac cycle, effectively reducing the interference of the heart, reliably identifying the time node when the saline contrast agent first reaches the lung area, and maintaining the original lung area to the greatest extent possible.

In the method of the present invention, it is proposed that breath-hold assessment is required before the test, which improves the efficiency of blood flow distribution assessment.

In the method of the present invention, a threshold of 20% is determined through screening to improve the quality of blood perfusion imaging, and based on this, the percentage of dead space ventilation, % of intrapulmonary shunt, and % of regional ventilation-blood flow matching (V/Q Macth %), which is more practical.

The method of the present invention can diagnose pulmonary embolism with a sensitivity of 90.9% and a specificity of 98.6%, and has high clinical application value.

Description of drawings

Figure 1 shows a graph of electrical impedance versus time;

Figure 2 shows the right heart image and pulmonary blood perfusion image, wherein A: right heart image; B: pulmonary blood perfusion image;

Figure 3 shows the ROC curve;

Figure 4 shows lung images of patient A with pulmonary embolism, wherein A: CT angiography of pulmonary angiography; B: image of pulmonary ventilation; C: image of pulmonary blood perfusion; D: image of pulmonary ventilation/blood flow distribution;

Figure 5 shows lung images of patient B with hemothorax, wherein A: lung CT angiography; B: lung ventilation image; C: pulmonary blood perfusion image; D: lung ventilation/blood flow distribution image.

Detailed ways

Before further describing the specific embodiments of the present invention, it should be understood that the protection scope of the present invention is not limited to the following specific specific embodiments; it should also be understood that the terms used in the examples of the present invention are for describing specific specific embodiments, It is not intended to limit the protection scope of the present invention. In the following examples, the test methods without specific conditions are usually in accordance with conventional conditions or in accordance with the conditions suggested by various manufacturers.

Example Construction and joint analysis of lung ventilation/blood flow distribution images

Measuring Cases and Data Collection

This study was approved by the ethics committee of our institution. The inclusion criteria were patients with clinically diagnosed respiratory failure and established central venous catheter injection drug therapy. Exclusion criteria for chest deformity or contraindications to electrical impedance monitoring (local skin lesions).

Patient information: 33 women, 50 men, mean age 62 years, mostly patients with respiratory failure.

Lübeck，Germany)采集，包含16个感应电极的EIT电极带放置于患者第四至第六肋间，参考电极置于腹部。电流激励模式为相邻激励模式，单幅EIT图像含有32×32个像素，每秒包含20帧图像。EIT图像的后续处理基于MATLABR2015b(Mathworks，Natick，Massachusetts，USA)。EIT raw data by PulmoVista 500 (

Lübeck, Germany) acquisition, the EIT electrode strip containing 16 sensing electrodes was placed in the fourth to sixth intercostal space of the patient, and the reference electrode was placed in the abdomen. The current excitation mode is adjacent excitation mode, a single EIT image contains 32 × 32 pixels, and contains 20 images per second. Subsequent processing of EIT images was based on MATLABR2015b (Mathworks, Natick, Massachusetts, USA).

First, the breath-hold test requires a minimum of 8 seconds (when the ventilator is mechanically ventilated, appropriate sedation first, adjust the ventilator to the fully controlled ventilation mode, press the exhale or inspiratory breath-hold button for 10s; self-restrained breathing patients are instructed to hold their breath for 8 seconds ); after the breath-hold test is passed, saline contrast EIT examination can be performed.

Then, the patient is connected to the pulmonary electrical impedance monitoring instrument, prepare 10ml of 10% NaCl, and confirm that the patient has established a central venous catheter (internal jugular vein or subclavian vein catheter can be used). 3) Saline injection: Generally, 2 operators are required to complete it together. One of them confirms that the EIT machine is working normally and starts the patient's breath-holding and simultaneously issues a command to inject saline; Rapidly inject 10ml of 10% NaCl into the patient through an intravenous catheter; the EIT monitor turns on the recording mode during the entire operation, and continuously collects chest electrical impedance signal data 2 minutes before the injection of saline. The whole process requires at least 5 minutes, and the breath-holding period is completely recorded. The process by which injection of saline results in a decrease in lung resistance. Again, offline analysis of the resistance signal data, the analysis steps are as follows:

1. During the breath-holding period, the overall resistance curve begins to decrease as the starting point of saline entering the body (T0), and after one motion cycle, it acts as the starting point for saline entering the pulmonary blood vessels (T1), and the lowest point of the overall resistance acts as the end point (T2) for the saline passing through the pulmonary vessels. The resistance curve in the T0-T1 time period reflects the saline entering the right heart and does not reflect the pulmonary vascular perfusion. In order to reduce interference, the curve of this time period is not used in the analysis; the resistance-time change curve of each lung region in the T1-T2 time period is used. (Slope fitting) to construct the pulmonary blood perfusion image (Figure 1 and Figure 2); the pulmonary blood perfusion image is constructed as follows:

(1) Calculate the perfusion volume of the i-th pixel point ΔZ _i (t)=a _i t+b, time t is the time period of the regional resistance-time curve for the analysis, a _i is the slope of the fitting curve, and the local slope can reflect the The size of the perfusion volume;

(2) Lung perfusion image distribution map formula

where a _g * is the relative lung perfusion volume of the gth pixel, a is the slope of the fitted line of the regional resistance; N is the total number of pixels in the lung area. The obtained relative lung perfusion distribution image, the perfusion volume of each pixel as a percentage of the total perfusion volume;

2. The lung ventilation image is constructed by the lung resistance changes of at least 5 consecutive breathing cycles within 1 minute before injection; the construction formula of the lung ventilation image is as follows:

Among them, _Vi is the total pixel points of the ventilation graph, and the number of breathing cycles included in N; ΔZ _i , Ins is the relative resistance change in inspiration, ΔZ _i , Exp is the relative resistance change in exhalation;

3. After optimizing the 0-40% threshold, it is determined that the lung ventilation image and the pulmonary blood flow image are used as the threshold of 20% of the maximum pixel point to construct the lung ventilation/blood flow distribution image; the specific formula is as follows:

V _k ＞20％×max(V _K ), K∈[1,1024]

K is defined as a pixel with local ventilation,

P _g ＞20％×max(P _G ), G∈[1,1024]

g is defined as a pixel with local perfusion;

4. The combined parameters of ventilation and blood flow are obtained by fitting analysis of lung ventilation map and blood perfusion distribution area:

Dead space ventilation %: the percentage of the total area that is only ventilated but not perfused;

Intrapulmonary shunt %: the percentage of the total area that is only perfused but not ventilated;

Regional Ventilation-Flow Match % (V/Q Macth %): The percentage of the total area that has both perfusion and ventilation.

Studies have verified that the above method can effectively identify the abnormal distribution of pulmonary blood ventilation in patients with respiratory failure. Among the 83 critically ill patients included, 11 were diagnosed with acute pulmonary embolism, and 72 patients were not clinically diagnosed with pulmonary embolism. Using the relevant technical parameters of the present invention to diagnose acute pulmonary embolism with dead space ventilation%>30.37, the sensitivity is 90.9%, the specificity is 98.6%, and the diagnostic efficiency is significantly better than the traditional serological index DD dimer. The ROC curve is shown in Figure 3.

Typical cases:

Pulmonary embolism patient A, basic information: male, 59, acute respiratory failure after lung cancer surgery, diagnosed as acute pulmonary embolism.

Pulmonary CT angiography (Fig. 4A) showed pulmonary embolism, thrombus was seen in the right pulmonary artery, pulmonary ventilation image (Fig. 4B) was normal, pulmonary blood perfusion image (Fig. 4C) showed decreased right pulmonary blood flow, pulmonary ventilation/blood flow distribution The image (Fig. 4D) revealed an increase in right-sided dead space ventilation, consistent with the clinical diagnosis.

Hemothorax patient B, basic information: male, 40, respiratory failure, hemothorax caused by rupture of thoracic intercostal artery.

Lung CT angiography (Fig. 5A) showed left lower thoracic hemothorax, lung ventilation image (Fig. 5B) showed lack of left lower ventilation, pulmonary blood perfusion image (Fig. 5C) showed left lower ventilation lack, and lung ventilation/blood flow distribution image (Fig. 5D) Prompt left lower ventilation / blood flow are missing, consistent with the clinical diagnosis.

The above-mentioned embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above-mentioned embodiments. Those skilled in the art should understand that on the basis of the technical solutions of the present invention, those skilled in the art do not need to Various modifications or deformations that can be made with creative work are still within the protection scope of the present invention.

Claims (10)

1. A bedside saline contrast-based pulmonary ventilation-perfusion electrical impedance tomography method, the method comprising the steps of:

(1) breath hold tests, requiring a minimum of over 8 seconds;

(2) injecting saline water to perform pulmonary blood perfusion radiography, and continuously acquiring the change of electrical impedance signals of the chest;

(3) performing off-line analysis on the resistance signal data;

preferably, the specific operation of step (1) is as follows: breath hold test, requiring a minimum of more than 8 seconds: when the breathing machine is used for mechanical ventilation, pressing an expiration or inspiration breath-hold key 10 s; the spontaneous breathing patient orders to hold breath for 8 seconds; after the breath holding test is passed, saline angiography EIT examination can be carried out;

preferably, the concentration of the injection saline is 10%, and the injection amount is 10 ml;

more preferably, the specific operation of step (2) is as follows: connecting a test subject with a pulmonary electrical impedance monitoring instrument, preparing 10% NaCl10ml, and confirming that a central venous catheter is established for the patient; after breath holding is started, injecting 10% NaCl10ml from a central venous catheter into the body to carry out pulmonary blood flow perfusion radiography; continuously collecting the change of the electrical impedance signals of the chest at the beginning of 2 minutes before the injection of the saline;

preferably, the step (3) of performing off-line analysis on the resistance signal data includes:

a. constructing a lung blood flow perfusion image;

b. constructing a lung ventilation image;

c. a lung ventilation/blood flow distribution image is constructed.

2. The method of claim 1, wherein the operation of step a comprises: the beginning of the overall resistance curve during breath holding period is named as the starting point of saline entering the body, namely T0, the starting point of saline entering pulmonary vessels is named as T1 after one cardiac cycle, the lowest point of the overall resistance is named as the end point of saline passing pulmonary vessels, namely T2, and the resistance curve of the time period of T0-T1 reflects the saline entering the right heart; pulmonary perfusion images were constructed by slope fitting using the resistance-time variation curves of the various lung regions for the T1-T2 time periods.

3. The method of claim 1, wherein the operation of step b comprises: lung ventilation image construction was performed by changes in lung resistance over at least 5 consecutive respiratory cycles within 1 minute prior to injection.

4. The method of claim 1, wherein the operations of step c comprise: the lung ventilation image and the lung blood flow perfusion image take 20% of the maximum pixel points as a threshold value to construct a lung ventilation/blood flow distribution image.

5. An image monitoring device, characterized in that the device comprises an image processor responsible for generating a lung ventilation image, a lung blood perfusion image from lung ventilation impedance data, lung blood perfusion impedance data; the image processor generating an image from the impedance data according to the method of any one of claims 1-4;

preferably, the device comprises a data receiver which is responsible for receiving the lung ventilation impedance data and the lung blood perfusion impedance data measured by the lung electrical impedance monitoring instrument; the data receiver is connected with the image processor.

6. The apparatus of claim 5, further comprising a controller responsible for controlling display of at least one of a lung ventilation image, a lung blood perfusion image according to a screen mode and a measurement site.

7. The apparatus of claim 6, wherein the controller comprises an image and waveform output control module, an impedance measurement control module, and an information determination and transmission module;

the image and waveform output control module may be configured to control display of at least one of a lung ventilation image, a lung blood flow perfusion impedance image, and a lung ventilation/blood flow distribution image according to a preset screen mode or a measurement site of a subject desired to be monitored;

the impedance measurement control module may be configured to control the electrical impedance monitoring instrument to measure lung ventilation impedance data, lung blood flow perfusion impedance data at the chest of the subject;

the information determination and transmission module may be configured to control features implemented by the data receiver and the image processor and transmit the received lung ventilation impedance data, lung blood flow perfusion impedance data, to the image processor to enable the lung ventilation impedance data, lung blood flow perfusion impedance data to be generated as an image.

8. An image monitoring system, characterized in that the system comprises the image monitoring device of any one of claims 5-7; preferably, the system further comprises a pulmonary electrical impedance monitoring instrument.

9. A method of diagnosing pulmonary embolism, the method comprising constructing a lung ventilation/blood flow distribution image by the method of claim 1, calculating a% dead space ventilation, and diagnosing pulmonary embolism when% dead space ventilation > 30.37%.

10. A pulmonary embolism diagnosis system, characterized in that the system comprises a diagnosis device, which performs the method of claim 9; preferably, the system further comprises an image monitoring device of any one of claims 5-7; more preferably, the system further comprises a pulmonary electrical impedance monitoring instrument.

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