Method for evaluating respiratory muscle movement function of IPF patient based on dynamic MRI and application

Abstract

The invention belongs to the technical field of medicine, and particularly relates to a method and application for evaluating the respiratory muscle movement function of an IPF patient based on dynamic MRI. Performing dynamic MRI processing on the to-be-tested person to obtain a lung dynamic MRI image; manually marking and segmenting an end-expiratory image and an end-inspiratory image on the lung dynamic MRI image along the inner edge of the thoracic cavity outline, and checking and correcting; obtaining evaluation parameters of chest wall movement and evaluation parameters of diaphragm movement and form by using the images; measuring parameters are analyzed, and the pulmonary fibrosis degree and pulmonary vessel and chest wall muscle parameters of the HRCT image are quantified; and comparing and statistically analyzing the parameters of different to-be-tested persons so as to evaluate the respiratory muscle movement function of the IPF patient. The dynamic MRI technology is adopted, and a quantitative basis is provided for evaluating the respiratory muscle dysfunction and severity of the IPF patient.

Description

Technical Field

[0001] The present invention belongs to the field of medical technology, and particularly relates to a method and application for evaluating the respiratory muscle motor function of IPF patients based on dynamic MRI. Background Art

[0002] Idiopathic pulmonary fibrosis (IPF) is the most common chronic, progressive, fibrotic interstitial lung disease (ILD), which is prone to occur in the middle-aged and elderly population. The pathological type and imaging type are usual interstitial pneumonia. The pulmonary function shows progressive restrictive ventilatory dysfunction. The clinical features include the progressive deterioration of exercise endurance, accompanied by the decline of the patient's quality of life. The treatment means are limited, and the prognosis of the patient after diagnosis is poor.

[0003] The chest wall muscle volume and mass of IPF patients are significantly lower than those of the healthy control group. Other research reports show that the cross-sectional area of the quadriceps femoris, the peripheral skeletal muscle of ILD patients, decreases by 20%, and at the same time, the strength of the quadriceps femoris also decreases by 18 - 35% compared with the predicted value, which is related to the decline of the patient's exercise endurance. Ebihara and his colleagues found that by measuring the limb skeletal muscle mass index, the cross-sectional area of the pectoralis major and erector spinae muscles of IPF patients, these indicators have good correlations with pulmonary function, peripheral muscle strength, six-minute walk distance, and quality of life scores. In addition, by measuring the cross-sectional area of the pectoralis major muscle of ILD patients, it is correlated with the parameters of the whole body mass and pulmonary function measured by dual-source energy spectrum CT, and is also related to the all-cause mortality and poor prognosis of the patients.

[0004] Respiratory muscles are important skeletal muscles that make up the respiratory system. Among them, the diaphragm is the main respiratory muscle, and normal diaphragmatic motor function is crucial for the ventilation process. Stephan et al. found that ILD patients have inspiratory muscle dysfunction, especially diaphragmatic dysfunction, through phrenic nerve stimulation. In addition, some studies have found through ultrasound imaging that the diaphragmatic displacement and thickness of ILD patients are smaller than those of healthy volunteers, and there is a positive correlation with pulmonary function.

[0005] Currently, the gold standard for measuring diaphragmatic function is to measure the transdiaphragmatic pressure. However, this examination is invasive, time-consuming, and requires high technical requirements. It needs to place esophageal and gastric balloons and special equipment for phrenic nerve stimulation, which is relatively difficult to implement in practice. Minimally invasive or non-invasive methods are more widely used in clinical practice. Non-invasive examinations for evaluating diaphragmatic function commonly use ultrasound, chest radiograph or fluoroscopy, computed tomography (CT), and magnetic resonance imaging (MRI). In recent years, due to the advantages of magnetic resonance examination such as radiation-free, three-dimensional positioning, high contrast resolution, and minimal invasiveness, it has been recognized by more scholars. A large number of studies have proved that the fast gradient echo (GRE) magnetic resonance (MR) pulse sequence can reliably evaluate diaphragmatic function and has good application prospects in studying normal and abnormal respiratory mechanics.

[0006] The multi-planar imaging technique of dynamic magnetic resonance imaging (MRI) can visually display the movements of the diaphragm and chest wall during the respiratory cycle without ionizing radiation. Many studies have confirmed that the diaphragm movement measured by dynamic MRI plays an important role in evaluating the disease progression and treatment effect of idiopathic scoliosis and neuromuscular diseases. At the same time, the evaluation of the structure and movement of the diaphragm and chest wall is also often applied to the study of the respiratory mechanics characteristics of healthy people and some chronic respiratory diseases, such as chronic obstructive pulmonary disease (COPD) and asthma. Since restrictive respiratory dysfunction is the main feature of the lung function of IPF patients, the change of the diaphragm and chest wall movement in IPF patients evaluated by dynamic MRI has not been reported. Summary of the Invention

[0007] The purpose of the present invention is to provide a method and application for evaluating the respiratory muscle movement function of IPF patients based on dynamic MRI, which is expected to provide a quantitative basis for evaluating the respiratory muscle dysfunction and severity of IPF patients.

[0008] The purpose of the present invention is achieved by the following technical solutions:

[0009] The present invention provides a method for evaluating the respiratory muscle movement function of IPF patients based on dynamic MRI, including the following steps:

[0010] (1) Measuring the lung function parameters of the subject to be tested;

[0011] (2) Performing dynamic MRI scanning on the subject to be tested to obtain images of the lungs in dynamic MRI;

[0012] (3) Manually marking and segmenting the images at the end of exhalation and end of inhalation along the inner edge of the thoracic cavity contour on the images of the lungs in dynamic MRI, and performing inspection and correction;

[0013] (4) Obtaining evaluation parameters of chest wall movement and evaluation parameters of diaphragm movement and morphology by using the above images;

[0014] (5) Analyzing the measured parameters and quantitatively analyzing the degree of pulmonary fibrosis, pulmonary blood vessels and chest wall muscle parameters in the HRCT images;

[0015] (6) Comparing and statistically analyzing the parameters obtained by the above steps (1)-(5) for different subjects to be tested, and further evaluating the respiratory muscle movement function of IPF patients.

[0016] Further, in step (1), the lung function parameters include the percentage of the forced expiratory volume in the first second of the subject to be tested accounting for the predicted value, the percentage of the forced vital capacity accounting for the predicted value, the ratio of the forced expiratory volume in the first second to the forced vital capacity, the percentage of the total vital capacity accounting for the predicted value, and the percentage of the carbon monoxide diffusion rate accounting for the predicted value.

[0017] Further, in step (2), the dynamic MRI scan is performed on three different levels in the coronal plane, the right sagittal plane, and the axial plane; the three levels in the axial plane are located at the aortic arch level, the carina level, and the right hepatic dome level respectively; the coronal plane is located at the coronal plane passing through the tracheal bifurcation, and the right sagittal plane is at the level passing through the apex of the lung and the right hepatic dome in the coronal plane positioning.

[0018] Further, in step (3), the reference point markers for manual annotation and segmentation are marked along the inner margin of the chest wall at the most ventral, most dorsal, most left, and most right positions of the axial images respectively; on the coronal images, they are marked at the apex of the lung and the highest point of the diaphragmatic dome; on the right sagittal images, they are marked at the apex of the lung, in front of the diaphragm, at the diaphragmatic dome, and behind the diaphragm.

[0019] Further, in step (4), the evaluation parameters of chest wall movement include the anteroposterior diameter, the left - right diameter, and the thoracic cavity area on the axial images, and the evaluation parameters of diaphragmatic movement and morphology include the cranio - caudal diameter on the coronal images, the area on the coronal images, the cranio - caudal diameter on the right sagittal images, the area on the sagittal images, the sub - diaphragmatic height, and the area.

[0020] Further, in step (5), the analysis and measurement parameters include: measuring the diameter values at the end - expiration and end - inspiration in all 40 frames of MRI images collected within 16 seconds for each phase, then calculating the average values at the end - expiration and end - inspiration respectively, and using the ratio between the average values at the end - inspiration and end - expiration and the thoracic area ratio to represent the characteristic parameters of the chest wall and diaphragmatic movement; the related parameters of the pulmonary vessels include the total pulmonary vessel volume, the pulmonary artery volume, the pulmonary vein volume, the total number of pulmonary vessel branches, the number of pulmonary artery branches, the number of pulmonary vein branches, the total curvature of the pulmonary vessels, the curvature of the pulmonary artery, the curvature of the pulmonary vein, the extra - thoracic muscle volume, density, and mass.

[0021] Further, in step (6), during the statistical analysis process, unpaired t - tests and Mann - Whitney U - tests are used for continuous variables, Fisher's exact test or chi - square test is used for categorical variables, Spearman correlation coefficient is used to analyze the correlation between clinical indicators and MRI indicators, the analysis is performed using the IBM SPSS 26.0 statistical analysis software, and graphing is done using the GraphPad Prism 9.0 software. A p value ≤ 0.05 is considered to have statistical significance.

[0022] The present invention also provides an application of the respiratory muscle motor function evaluation result obtained by using the above method in judging the severity of IPF. The respiratory muscle motor function is correlated with TLV, FVC%, FEV%, TLC%, DLco%, 6-MWD, the volume and mass of chest wall muscles, and the manifestation of dyspnea. At the same time, it is also correlated with the volume, the number of branches, and the curvature of pulmonary blood vessels. There is a correlation between the parameters for evaluating the respiratory muscle motor function and the parameters for evaluating the severity of IPF.

[0023] Further, the parameters of the respiratory muscle motor function include the anteroposterior diameter, the left-right diameter, the cranio-caudal diameter, and the ratio of the thoracic cavity area of the MRI image parameters of the chest wall and diaphragm movements; the parameters for evaluating the severity of IPF include TLV, FVC%, FEV%, TLC%, DLco%, 6-MWD, the volume and mass of chest wall muscles, the dyspnea score, the total pulmonary blood vessels, the curvature, the pulmonary artery, and the number of branches of the pulmonary vein.

[0024] Further, the anteroposterior diameter, the left-right diameter, the cranio-caudal diameter, and the ratio of the thoracic cavity area of the MRI image parameters of the chest wall and diaphragm movements are positively correlated with the total pulmonary blood vessels, the pulmonary artery, and the number of branches of the pulmonary vein, and are negatively correlated with the curvature.

[0025] The beneficial effects of the present invention are as follows:

[0026] The research of the present invention shows that the main characteristics of respiratory muscle dysfunction in IPF patients are the reduction of the diaphragmatic dome, the posterior part of the diaphragm, and the movement of the dorsal and ventral chest walls during deep breathing. At the same time, the movements of the diaphragm and chest wall are related to the reduction of the volume and mass of chest wall muscles, the deterioration of lung function, the decline of exercise tolerance, and the reduction of pulmonary blood vessels. Dynamic MRI is expected to provide a quantitative basis for evaluating the respiratory muscle dysfunction and severity in IPF patients. Brief Description of the Drawings

[0027] Figure 1 It is a multi-planar imaging diagram of dynamic MRI. The axial plane includes the aortic arch (a), the carina (b), and the hepatic dome level (c), the coronal plane passing through the tracheal bifurcation (d), and the right sagittal plane passing through the apex of the lung and the hepatic dome (e);

[0028] Figure 2 It is a segmentation diagram of dynamic MRI images at the end of exhalation and the end of inspiration. At the end of exhalation (a) and the end of inspiration (d), it is segmented along the inner edge of the chest wall in the axial MRI image; at the end of exhalation (b) and the end of inspiration (e), it is segmented along the inner edge of the chest wall in the right sagittal plane; at the end of exhalation (c) and the end of inspiration (f), it is segmented along the inner part of the chest wall in the coronal plane;

[0029] Figure 3 It is a schematic diagram of reference point marking;

[0030] Figure 4Schematic diagram for measuring the moving diameters of the chest wall and diaphragm. RAP, anteroposterior diameter of the right thoracic cavity in the axial plane; LAP, anteroposterior diameter of the left thoracic cavity in the axial plane; LR, left-right diameter of the thoracic cavity in the axial plane; RCC, cranio-caudal diameter of the right lung in the coronal plane; LCC, cranio-caudal diameter of the left lung in the coronal plane; AND, linear distance between the apex of the lung and the anterior diaphragm in the sagittal plane; APD, linear distance between the apex of the lung and the top of the diaphragm in the sagittal plane; POD, linear distance between the apex of the lung and the posterior diaphragm in the sagittal plane;

[0031] Figure 5 Schematic diagram for measuring the shape of the diaphragm. The height (DH) and area (DA) under the diaphragm are shown in Figure (a). The definition of DH is the vertical distance between the top of the diaphragm and the connecting line of the anterior and posterior angles of the diaphragm. The definition of DA is the area between the diaphragm and the connecting line of the anterior and posterior angles of the diaphragm. The height (DH) and area (DA) of the diaphragm at the end of exhalation (b), and the height (DH) and area (DA) of the diaphragm at the end of inhalation (c);

[0032] Figure 6 Schematic diagram of dynamic MRI images during free breathing in the coronal plane of a healthy control (male, 58 years old, BMI = 24.1) (a, c) and a patient with IPF (male, 58 years old, BMI = 25.5) (b, d) during quiet breathing and deep breathing;

[0033] Figure 7 Schematic diagram of dynamic MRI images during free breathing in the right sagittal plane of a healthy control (male, 58 years old, BMI = 24.1) (a, c) and a patient with IPF (male, 58 years old, BMI = 25.5) (b, d) during quiet breathing and deep breathing;

[0034] Figure 8 Box plot comparison of the ratios of the left anteroposterior diameter (LAP), right anteroposterior diameter (RAP), left-right diameter (LR), and chest area (A) at the levels of the aortic arch (The arcus aorta level) (a), tracheal carina (The tracheal carina level) (b), and right diaphragmatic dome (The diaphragm dome level) (c) in the axial plane between patients with IPF and healthy controls during deep breathing. * indicates p < 0.05, suggesting that the difference is statistically significant;

[0035] Figure 9Box plot comparison of the ratio of diameter to area in the coronal plane (The coronal plane) (a) and the right sagittal plane (The right sagittal plane) (b) between IPF patients and healthy controls during deep breathing. LCC, left cranio-caudal diameter; RCC, right cranio-caudal diameter; CA, coronal thoracic area; AND, APD, POD are the distances from the apex of the lung to the anterior, apical, and posterior diaphragms in the sagittal plane, respectively; DH, height below the diaphragm; DA, area below the diaphragm; * indicates p < 0.05, considered to be statistically significant;

[0036] Figure 10 Area-time curve graphs of the chest wall during quiet breathing and deep breathing. The amplitude of the curves in the coronal plane (a) and the right sagittal plane (b) of IPF patients during quiet breathing is slightly lower than that of the healthy control group; the amplitude of the curves in the coronal plane (c) and the right sagittal plane (d) of IPF patients during deep breathing is significantly lower than that of the healthy control group. Detailed implementation manners

[0037] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation embodiments of the present invention.

[0038] It should be understood that the terms described in the present invention are only for describing specific implementation manners and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0039] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0040] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific implementation manners of the present invention specification, which are obvious to those skilled in the art. Other implementation manners obtained from the present invention specification are obvious to those skilled in the art. The present invention specification and examples are only exemplary.

[0041] As used herein, terms such as "comprising", "including", "having", "containing", etc. are all open-ended terms, meaning including but not limited to.

[0042] Example 1

[0043] I. General Information

[0044] In this example, 96 stable IPF patients (92 males and 4 females, with an average age of 61±7) who were hospitalized in the Department of Respiratory and Critical Care Medicine of our hospital from August 2020 to August 2022 and diagnosed through multidisciplinary discussion were prospectively included, as well as 50 healthy controls (46 males and 4 females, with an average age of 58±6) matched by age and gender. All patients underwent HRCT, pulmonary function, and MRI examinations within one week. General information of all subjects was collected, including gender, age, smoking history, height, weight, body mass index (BMI), pulmonary function parameters, six-minute walk distance (6-MWD), quantitative lesion range, health-related quality of life score, and dyspnea score.

[0045] Inclusion and exclusion criteria for this example: (1) Disease group: 1) Inclusion criteria: ① Referring to the diagnostic criteria for IPF of the American Thoracic Society / European Respiratory Society / Japanese Respiratory Society / Latin American Thoracic Society (ATS / ERS / JRSALAT) in 2018 edition, IPF patients diagnosed through multidisciplinary discussion based on the patient's clinical manifestations, chest HRCT, with or without pathology. 2) Exclusion criteria: ① Complicated with other pulmonary diseases or malignant tumors of other tissues; ② Unstable cardiovascular diseases, such as acute coronary syndrome, congestive heart failure, uncontrolled hypertension; ③ Neuromuscular diseases, such as Pompe disease and Duchenne muscular dystrophy; ④ Without HRCT of our hospital or unable to complete pulmonary function and six-minute walk distance tests; ⑤ Having MRI contraindications such as implanted metal materials in the body, such as stents, intrauterine devices, hip replacement, etc., and unable to perform MRI examination; ⑥ Patients who cannot perform deep breathing or fail in MRI and pulmonary function examinations.

[0046] (2) Healthy control group: Healthy non-smoking adults in this region were selected. General information of all subjects was collected, including gender, age, height, weight, body mass index (BMI), and pulmonary function. 1) Inclusion criteria: ① Aged 45-76 years old; ② No history of chronic respiratory system, cardiovascular system, and related surgeries in the past; ③ Pulmonary function examination: FEV1 / FVC%>.70, percentage of FEV1 predicted value (FEV%pre)>0.8, and percentage of DLco predicted value (DLco%pre)>0.8; ④ No diseases such as liver, nerve, or other organ tumors; ⑤ Voluntarily participating in this study. Approved by the Ethics Committee of China-Japan Friendship Hospital (2019—123-K85—1), and written informed consent forms were obtained from each subject.

[0047] II. Research Methods

[0048] 1. Check instrument parameters

[0049] (1) Pulmonary function: Pulmonary function was measured strictly in accordance with the pulmonary function measurement standards of the American Thoracic Society / European Respiratory Society (ATS / ERS) (MasterScreen, Vyaire Medical GmbH, Hoechberg, Germany). The MasterScreen pulmonary function instrument of Vyaire Medical Company in Germany was used for the measurement. The whole process of the measurement was independently completed by professional technicians with more than 10 years of clinical work experience in the pulmonary function room in the examination room. The subjects were asked to sit upright on a chair with a backrest, keeping their necks and chests in a straight line. The parameters measured for pulmonary function included: percentage of forced expiratory volume in the first second as a percentage of the predicted value (FEV% pre), percentage of forced vital capacity as a percentage of the predicted value (FVC% pre), ratio of forced expiratory volume in the first second to forced vital capacity (FEV1 / FVC%), percentage of total vital capacity as a percentage of the predicted value (TLC% pre), and percentage of carbon monoxide diffusing capacity as a percentage of the predicted value (DLco% pre).

[0050] (2) HRCT: All patients underwent HRCT scans using multi-detector row spiral scanners (Lightspeed VCT / 64, GE Healthcare, Chicago, IL, USA; Toshiba Aquilion ONE TSX-301C / 320, Toshiba, Tochigi, Japan; Philips iCT / 256, Philips, Amsterdam, Netherlands). The specific scanning methods and parameters were the same as those in the first part.

[0051] (3) MRI: All patients underwent MRI examinations on a 1.5T MRI scanner (MAGNETOM Area, Siemens Healthcare, Erlangen, Germany) using 18-channel and 12-channel phased array surface coils. The main parameters were as follows: Repetition time (TR) = 868 ms, Echo time (TE) = 46 ms, Flip angle (FA) = 160°, Field of view (FOV) = 340 mm × 480 mm, Resolution = 0.8 mm × 0.8 mm × 10.0 mm. A total of 6 slices were scanned, with 40 frames scanned for each slice, 0.4 s for each frame, for a total of 3 - 4 minutes. The specific scanning method: Free-breathing dynamic MRI was scanned using a parallel imaging accelerated two-dimensional dynamic fast gradient echo sequence. The patients were in the supine position, with their hands together on both sides of the body, and they were instructed to breathe during the scanning process. A respiratory belt was used to fix the respiratory pad on the right upper abdomen to monitor whether the subjects cooperated with the breathing instructions for calm and deep breathing. As Figure 1 shown, dynamic MRI scans were performed on 3 different slices in the coronal, right sagittal, and axial planes respectively. The 3 axial slices were located at the level of the aortic arch ( Figure 1 a in), the level of the carina ( Figure 1 b in), and the level of the right hepatic dome ( Figure 1 c in). The coronal slice was located at the coronal plane passing through the tracheal bifurcation ( Figure 1 d in). The right sagittal slice was located at the slice passing through the apex of the lung and the right hepatic dome in the coronal plane ( Figure 1 e in). To avoid the influence of the cardiac contour and motion on the results, the right sagittal plane was selected for analysis. For each imaging plane, MRI obtained the respiratory motion (3 - 4) during multiple respiratory cycles within 16 seconds at rest and during deep breathing ( Figure 2 ) in the free-breathing state. The total scanning time was 4 - 5 min. All patients underwent respiratory motion training for calm and deep breathing before the scan.

[0052] 2. MRI Image Segmentation and Reference Point Annotation

[0053] The image processing of pulmonary dynamic MRI was performed using InferScholar software ( https: / / www.infer- vision.com)This was carried out by two radiologists with rich experience in chest imaging diagnosis (Observer 1 had 20 years of work experience; Observer 2 had 7 years of work experience). The radiologist Observer 2 manually marked and segmented the images at the end of exhalation and at the end of inspiration along the inner edge of the thoracic cavity contour on the dynamic MRI images of multi-planar imaging (axial aortic arch, carina, and right hepatic dome levels, coronal plane passing through the tracheal bifurcation, and right sagittal plane passing through the apex of the lung and the hepatic dome). Figure 2 )The radiologist Observer 1 checked and corrected the images marked by Observer 2.

[0054] As Figure 3 shown, the reference point markers were respectively marked on the axial images at the most ventral (anterior, Anterior), most dorsal (posterior, Posterior), most left (left, Left), and most right (right, Right) along the inner edge of the thoracic cage; on the coronal images at the apex of the lung (cranial, Cranial) and the highest point of the diaphragmatic dome (caudal, Caudal); on the right sagittal images at the apex of the lung and in front of the diaphragm (anterior, Anterior), the diaphragmatic apex (apex, Apex), and behind the diaphragm (posterior, Posterior). The radiologist Observer 2 marked the points on the segmented images according to the definition of the reference points, and the radiologist Observer 1 checked and corrected all the marked points.

[0055] 3. Evaluation parameters of chest wall movement

[0056] The parameters for evaluating chest wall movement include the anteroposterior diameter (Anterior-posterior, AP), the left-right diameter (Left-right, LR), and the thoracic area (Area) on the axial images (aortic arch, carina, and right hepatic dome levels).

[137] As Figure 4 shown in a, the distance of the anteroposterior diameter (AP) is defined as the longest distance from the dorsal side to the ventral side of the thoracic cavity, that is, the vertical distance from point A to point p, including the left anteroposterior diameter (LAP) and the right anteroposterior diameter (RAP). The distance of the left-right diameter (LR) is defined as the longest distance from the right inner edge to the left inner edge of the thoracic cavity. The thoracic area of the points on the axial images is defined as the sum of the areas of the two lungs after segmentation.

[0057] 4. Evaluation parameters of diaphragmatic movement and morphology

[0058] Parameters for evaluating diaphragmatic movement: As Figure 4 shown in b, the cranio-caudal diameter (Cranial-caudal, CC) on the coronal images, that is, the vertical distance from the apex of the lung to the bilateral diaphragmatic domes, is divided into the left cranio-caudal diameter (LCC) and the right cranio-caudal diameter (RCC). The area on the coronal images is defined as the sum of the areas of the two lungs after segmentation. As Figure 4As shown in c, the cranio-caudal diameters on the right sagittal images were defined as the distances from the apex of the lung to the anterior diaphragm (AND), the apex of the diaphragm (APD), and the posterior diaphragm (POD), respectively. The area on the sagittal image was defined as the area of the segmented right sagittal image.

[0059] Evaluation of diaphragmatic morphology: As Figure 5 shown, the parameters describing diaphragmatic morphology included the sub-diaphragmatic height (DH) and area (DA). The sub-diaphragmatic height (DH) was defined as the vertical distance from the highest point of the diaphragm to the anterior-posterior line of the diaphragm. The sub-diaphragmatic area (DA) was defined as the area between the contour of the diaphragm and the anterior-posterior line of the diaphragm.

[0060] 5. Analysis method of measurement parameters

[0061] The 40 frames of MRI images collected within 16 seconds for each phase contained 2 - 4 respiratory cycles. The linear values at the end of expiration and inspiration in all 40 frames of images were measured, and then the average values at the end of expiration and inspiration were calculated separately for further analysis. Finally, the characteristic parameters of the movement of the chest wall and diaphragm were represented by the ratios between the average values at the end of inspiration and expiration, such as AP, LR, CC, and the ratio of the chest area.

[0062] Respiratory curve construction: Observe the characteristic differences in the continuous respiratory movement states of quiet breathing and deep breathing between healthy controls and IPF patients. The respiratory curves were constructed by extracting the areas of 40 frames of coronal and sagittal MRI images of one healthy control and one IPF patient with exactly matched age and gender in the states of quiet breathing and deep breathing for description.

[0063] 6. Quantification of pulmonary fibrosis degree in HRCT images

[0064] The segmentation of HRCT images of healthy controls and IPF patients was performed on the InferScholar software ( https: / / www.infer-vision.com ), and the specific method was the same as that in the first part.

[0065] 7. Pulmonary vascular and chest wall muscle parameters in quantitative HRCT images

[0066] Transfer the de-identified HRCT images in Digital Imaging and Communications in Medicine (DICOM) format to the digital lung workstation (FACTAI + digital Lung V1.0, Shenzhoudexin Medical Imaging Technology Co., Ltd.). The measured parameters include the measured vascular-related parameters, including: total pulmonary vascular (TPV) volume, pulmonary artery (PAV) volume, pulmonary vein (PVV) volume, total number of pulmonary vascular branches, number of pulmonary artery branches, number of pulmonary vein branches, total pulmonary vascular tortuosity, pulmonary artery tortuosity, pulmonary vein tortuosity, extrapleural muscle volume, density, and mass.

[0067] 8. Statistical analysis

[0068] Compare the data between IPF patients and healthy controls. Unpaired t-tests and Mann-Whitney U-tests were used for continuous variables, and Fisher's exact test or chi-square test was used for categorical variables. Spearman correlation coefficients were used to analyze the correlations between clinical indicators and MRI indicators. Analyses were performed using IBM SPSS 26.0 statistical analysis software (IBM Corp., Armonk, NY, USA), and graphs were plotted using GraphPad Prism 9.0 software. A p value ≤ 0.05 was considered statistically significant.

[0069] III. Research results

[0070] (I) Demographic and clinical characteristics

[0071] As shown in Table 1, a total of 96 IPF patients were finally enrolled in this example. Among them, 92 were male patients (95.8%) and 4 were female patients (4.2%). The average age was 62 ± 7 years. There were 50 healthy controls, including 46 male (92.0%) and 4 female (8.0%). The average age was 58 ± 6 years, and there was no significant difference in age (p = 0.057). There were more smokers in the IPF patient group (83.3%) than in the healthy control group (32.0%) (p < 0.001). There were no significant differences in height, weight, and BMI between the IPF patient group and the healthy control group (p > 0.05). The total lung volume (TLV = 4.3 ± 0.9) of IPF patients was significantly smaller than that of healthy controls (TLV = 4.7 ± 0.5, p = 0.013).

[0072] The predicted FVC% in IPF patients was 82.9±16.6 and the predicted DFEV% was 86.0±15.8, lower than the predicted FVC% (103.3±11.0, p<0.001) and the predicted FEV% (99.1±12.5, p<0.001) in healthy controls. However, there was no statistical difference in FEV1 / FVC% between the two groups. The predicted TLC% (IPF patients vs. healthy controls: 69.4±13.9 vs. 98.5±9.7, p<0.001) and the predicted DLco% (IPF patients vs. healthy controls: 54.9±17.3 vs. 100.0±14.1, p<0.001) also showed significant statistical differences between the two groups.

[0073] The thoracic wall muscle volume (4.7 L) and mass (5.5 kg) in PF patients were significantly lower than those in healthy controls (volume: vs. 5.3 L, p = 0.005; mass: vs. 6.3 kg, p = 0.007). There was only a difference in the thickness of the right anterior part of the diaphragm between the two groups, and it was significantly higher in the disease group (4.6 mm) than in healthy controls (vs. 5.3 mm, p = 0.020). The thickness of the left side of the diaphragm was also higher in the patient group than in healthy controls, although there was no statistical difference. On the contrary, only the thickness of the posterior right side of the diaphragm was lower in the IPF patient group (3.3 mm) than in healthy controls (vs. 3.6 mm, p = 0.266).

[0074] Table 1 Demographics and clinical indicators of IPF patients and healthy control group

[0075]

[0076]

[0077] Note: * indicates p<0.05, considered to have statistical significance. 6MWD, six-minute walk distance; SpO 2 , lowest blood oxygen concentration; GGO, ground-glass opacity.

[0078] (II) Thoracic wall movement characteristics

[0079] As shown in Table 2, at rest, there were no statistical differences in the ratios of the left anteroposterior diameter, right anteroposterior diameter, left-right diameter, and thoracic cavity area at the aortic arch level, carina level, and right diaphragmatic dome level between IPF patients and healthy controls (p>0.05).

[0080] In the deep breathing state, the ratios of the left anteroposterior diameter to the right anteroposterior diameter at the aortic arch level, carina level, and right diaphragmatic dome level in IPF patients were significantly lower than those in the healthy control group (p < 0.001) (Table 2). At the same time, the thoracic cavity area values at the aortic arch, carina, and right diaphragmatic dome levels in the IPF patient group were also significantly smaller compared with the healthy control group (IPF vs. healthy control: 1.16 vs. 1.26, p < 0.001; 1.11 vs. 1.19, p < 0.001; 1.09 vs. 1.16, p < 0.001). However, there was no significant difference in the ratio of the left-right diameter between the IPF patients at the aortic arch, carina, and right diaphragmatic dome levels and the healthy control group.

[0081] Table 2 Comparison of chest wall movement characteristics between IPF patients and healthy controls during quiet breathing and deep breathing

[0082]

[0083] Note: * indicates p < 0.05, indicating that the difference is statistically significant.

[0084] (III) Diaphragmatic movement and morphological characteristics

[0085] As Figure 6 and Figure 7 shown are the diaphragmatic movement trend diagrams in the coronal and right sagittal planes at rest and during deep breathing in the IPF group and the healthy control group.

[0086] As shown in Table 3, during quiet breathing, there was no significant difference in the cranio-caudal diameter (CC, ANP, APD, POD) and thoracic cavity area (area) between the IPF patient group and the healthy control group in the coronal and right sagittal planes. During deep breathing, the ratios of the left cranio-caudal diameter (LCC: 1.20), right cranio-caudal diameter (RCC: 1.28), and area (area: 1.56) in the coronal plane of IPF patients were lower than those in the healthy control group (LCC: vs. 1.34, p < 0.001; RCC: vs. 1.42, p < 0.001; area: vs. 1.72, p < 0.002) ( Figure 4-9 ). In the right sagittal plane, the ratios of the cranio-caudal diameter of the diaphragmatic dome (APD: 1.20) and the posterior part of the diaphragm (POD: 1.23) in the IPF patient group were smaller than those in the healthy control group (APD: vs. 1.30, p < 0.001; POD: vs. 1.32, p < 0.001; area: vs. 1.60, p < 0.001). However, there was no significant difference in the ratio of the cranio-caudal diameter of the anterior part of the diaphragm (APD: 1.10) between the IPF patient group and the healthy control group (vs. 1.11, p = 0.062).

[0087] In addition, there were significant statistical differences in the right sagittal area ratio between the two groups (IPF vs healthy control: 1.60 vs. 1.38, p < 0.001)( Figure 8 ). For the parameters of the diaphragm morphology, there were no statistical differences in the height below the diaphragm and the ratio of the area below the diaphragm during quiet breathing between the IPF group (DH: 0.96; DA: 0.97) and the healthy control group (DH: vs. 0.96, p = 0.798; DA: vs. 0.97, p = 0.228). However, during deep breathing, the ratios of the height below the diaphragm (DH: 0.96) and the area (DA: 1.00) in the IPF patient group were increased compared with those in the healthy control group (DH: vs. 0.81, p < 0.001; DA: vs. 0.90, p < 0.001)( Figure 9 ), suggesting an increase in the diaphragm curvature.

[0088] As Figure 10 shown in the respiratory curves, which are the area-time curves of the coronal and sagittal planes. During quiet breathing, the curve amplitude of IPF patients was slightly lower than that of the control group( Figure 10 a and Figure 10 b). During deep breathing, the curve amplitude of IPF patients was significantly lower than that of the control group( Figure 10 c and Figure 10 d). By comparing the movement curve amplitudes of the two groups during quiet breathing and deep breathing, it was shown that the respiratory muscle movement reserve function of IPF patients was significantly weakened.

[0089] Table 3 Diaphragm movement and morphological characteristics between IPF patients and healthy controls

[0090]

[0091] Note: * indicates p < 0.05, indicating that the difference is statistically significant. CC is the cranio-caudal diameter; DH is the height below the diaphragm; DA is the area below the diaphragm; AND, APD, and POD are the distances from the apex of the lung to the anterior, top, and posterior of the diaphragm in the sagittal plane, respectively.

[0092] (IV) Correlation analysis of chest wall and diaphragm movement with disease severity

[0093] As shown in Table 4, in the deep breathing state, only the thickness behind the right diaphragm is correlated with the movement behind the right sagittal diaphragm (r =.270, p < 0.05), area (r = 0.243, p < 0.05), and the ratio of the area under the diaphragm (r = -0.283, p < 0.05). However, other parts of the diaphragm have no correlation with the movement parameters of the diaphragm and chest wall. The ratios of the anteroposterior diameter (AP), cranio-caudal diameter (CC), and thoracic cavity area (area) of the MRI image parameters representing chest wall movement and diaphragm movement in all planes are positively correlated with the chest wall muscle volume (0.251 - 0.469, p < 0.05) and mass (0.249 - 0.503, p < 0.05), but have no correlation with the area and height under the diaphragm. Similarly, the MRI image parameters representing chest wall movement and diaphragm movement in all planes have no correlation with the chest wall muscle density. In addition, the ratios of the anteroposterior diameter (AP), cranio-caudal diameter (CC), and thoracic cavity area (area) of the MRI image parameters representing chest wall movement and diaphragm movement in all planes are positively correlated with the total lung volume (TLV) (0.208 - 0.488, p < 0.05), FVC% predicted value (0.227 - 0.467, p < 0.05), FEV% predicted value (0.276 - 0.462, p < 0.05), TLC% predicted value (0.264 - 0.453, p < 0.05), DLco% predicted value (0.240 - 0.445, p < 0.05), and 6MWD (0.305 - 0.481, p < 0.05). However, only the parameters in the right sagittal position are related to SpO 2 (APD: 0.362, p < 0.05; POD: 0.367, p < 0.05; area: 0.338, p < 0.05) also show significant correlations.

[0094] In addition, the height under the diaphragm (DH) and the area under the diaphragm (DA) are negatively correlated with the total lung volume (TLV) (DH: -0.306, p < 0.05; DA: -0.281, p < 0.05), FVC% predicted value (DH: -0.385, p < 0.05; DA: -0.347, p < 0.05), FEV% predicted value (DH: -0.429, p < 0.05; DA: -0.378, p < 0.05), TLC% predicted value (DH: -0.395, p < 0.05; DA: -0.398, p < 0.05), and DLco% predicted value (DH: -0.309, p < 0.05; DA: -0.270, p < 0.05).

[0095] As shown in Table 5, there were statistically significant differences in the left-right diameter (LR), cranio-caudal diameter (LCC, APD), and thoracic area among IPF patients in different dyspnea groups (MRC1 vs. MRC2 vs. MRC3). However, all MRI parameters of chest wall and diaphragmatic movement were not correlated with the healthy quality of life score of IPF patients and the extent of fibrosis on HRCT. Nevertheless, the ratios of the anteroposterior diameter (AP), left-right diameter (LR), cranio-caudal diameter (CC), and thoracic area (area) of all MRI image parameters representing chest wall and diaphragmatic movement in Table 6 were positively correlated with the number of branches of total pulmonary vessels, pulmonary artery, and pulmonary vein (0.236 - 0.479, p < 0.05), and negatively correlated with the curvature [(-0.235)-(-0.514), p < 0.05]. Interestingly, the MRI image parameters representing chest wall movement had good correlations with the volumes of total pulmonary vessels (0.259 - 0.395, p < 0.05), pulmonary artery (0.239 - 0.283, p < 0.05), and pulmonary vein (0.263 - 0.406, p < 0.05). However, the MRI parameters representing diaphragmatic movement were not correlated with the vessel volumes, and the movement in front of the diaphragm was also not correlated with the vessel volume, the number of branches, and the curvature.

[0096] Table 4 Correlation between MRI parameters of chest wall and diaphragmatic movement in IPF patients and total lung volume, 6MWD, and lung function

[0097]

[0098]

[0099] Note: * indicates p < 0.05, suggesting that the difference is statistically significant. AND, APD, and POD are the distances from the apex of the lung to the front of the diaphragm in the sagittal plane, the top of the diaphragm, and the back of the diaphragm, respectively; DH is the height below the diaphragm; DA is the area below the diaphragm.

[0100] Table 5 Comparison of chest wall and diaphragmatic movement characteristics among different dyspnea score groups in IPF patients

[0101]

[0102]

[0103] Note: * indicates p < 0.05, suggesting that the difference is statistically significant. AND, APD, and POD are the distances from the apex of the lung to the front of the diaphragm in the sagittal plane, the top of the diaphragm, and the back of the diaphragm, respectively; DH is the height below the diaphragm; DA is the area below the diaphragm.

[0104] Table 6. Correlation between diaphragmatic and chest wall movement parameters and pulmonary vessel parameters

[0105]

[0106]

[0107] Note: * indicates that p < 0.05 is considered statistically significant. AND, APD, POD are the distances between the apex of the lung and the front of the diaphragm, the top of the diaphragm, and the back of the diaphragm in the sagittal plane, respectively; DH, height under the diaphragm; DA, area under the diaphragm. TPV, total pulmonary vascular; PAV, pulmonary artery; PVV, pulmonary vein.

[0108] in conclusion

[0109] This embodiment uses dynamic MRI to analyze the characteristics of chest wall movement and diaphragm movement function and morphology of IPF patients. The results show that although the chest wall movement and diaphragm movement function and morphology vary between the two groups during quiet breathing, the chest wall and diaphragm movement of IPF patients is significantly reduced compared with healthy controls under deep breathing, especially the anteroposterior diameter movement of the axial position, the cranio-caudal diameter of the coronal position, and the movement of the diaphragm top and posterior diaphragm in the right sagittal position, accompanied by an increase in the diaphragm curvature. In addition, the weakened diaphragm and chest wall movement indicators during deep breathing are correlated with TLV, FVC%, FEV%, TLC%, DLco%, 6-MWD, chest wall muscle volume and quality, and dyspnea symptoms, and are also correlated with the volume, number of branches, and curvature of the pulmonary vessels, but are not correlated with health-related quality of life (HRQoL) and the range of fibrosis lesions on HRCT images.

[0110] The diaphragm is the main inspiratory muscle of the human body, bearing 60%-80% of the ventilation needs. In addition to diaphragm dysfunction caused by neuromuscular diseases, with the deepening of research, more and more studies have found that chronic respiratory diseases can also cause diaphragm dysfunction. In people with COPD, diaphragm movement is related to airway obstruction, and diaphragm dysfunction in COPD patients is correlated with different lung function parameters (such as FEV% predicted value, FEV1 / FFVC%, FEV% and TLC% predicted value, etc.) and exercise tolerance. In addition, diaphragm dysfunction is related to acute exacerbation of COPD patients, and the assessment of diaphragm dysfunction has a high accuracy in predicting the outcome of patients' weaning and extubation. At the same time, animal models of COPD combined with diaphragm or skeletal muscle dysfunction have matured, and further mechanism studies have found that skeletal muscle dysfunction in COPD mice is related to muscle atrophy caused by factors such as spillover of pulmonary inflammatory response, oxidative stress and hypoxia.

[0111] In patients with ILD, diaphragmatic dysfunction is associated with systemic inflammation, disuse, hypoxia, corticosteroids, malnutrition, and overload due to lung tissue dysfunction. A study published in 2019 based on a bleomycin-induced mouse model of pulmonary fibrosis found increased activation of STAT3 and AMPK in skeletal muscle tissue, along with an increase in atrogin1 protein. A mouse myoblast model showed that IL-6 and IL-33 specifically activate the STAT3 and AMPK signaling pathways, respectively, inducing the expression of muscle-specific proteolytic markers MuRF1 and atrogin1. These results suggest that elevated levels of IL-6 and IL-33 in the serum of bleomycin-induced lung injury mice may lead to pulmonary fibrosis while reducing lung function and muscle mass by activating the STAT3 and AMPK signals. Similarly, a new concept has been proposed in the past two years that patients with IPF have sarcopenia, especially in advanced IPF patients, which may also be the reason for the diaphragmatic dysfunction in IPF patients, including skeletal muscle.

[0112] In studies on diaphragmatic movement in ILD patients, the current research results are inconsistent. Some researchers have shown by ultrasound or CT that the diaphragmatic movement displacement during deep breathing in ILD patients is reduced compared to the healthy control group. Conversely, He et al. found similar diaphragmatic movement between IPF patients and the healthy group by ultrasound. This example shows by dynamic MRI during free breathing that compared to the normal control group, the diaphragmatic movement in IPF patients during deep breathing is weakened, and the significantly weakened areas are the diaphragmatic dome and the posterior (dorsal) part of the diaphragm. Conversely, the movement of the anterior (ventral) part of the diaphragm is not significantly different from that of the healthy control. Analyzing the reasons, this may be related to the distribution of fibrosis because the lung lesions in IPF patients are mainly distributed subpleurally at the bases of both lower lungs. In addition to possible dysfunction of the diaphragm itself, the reduced contractile function of the lung tissue may also play a role. Additionally, based on studies of the respiratory muscles in the healthy population, it has been observed that the central and posterior parts of the diaphragm play a major role in the process of lung ventilation, while the anterior part of the diaphragm has a smaller role.

[0113] In addition, there has been no research report on the change characteristics of the diaphragmatic curvature in IPF patients so far. This example observed by MRI images in the right sagittal plane that the diaphragmatic curvature in IPF patients during deep inspiration increases, that is, both the diaphragmatic area (DA) and height (DH) are higher than those of the control group, which may be related to the reduction of lung volume caused by pulmonary fibrosis in IPF patients. In contrast, the diaphragmatic curvature in COPD patients decreases, and due to air trapping and airway obstruction, the lung volume increases, making the diaphragmatic curvature flatter. In addition to diaphragmatic movement, chest wall movement also contributes to active ventilation during the breathing process. This study found that the chest wall movement in IPF patients during deep breathing significantly decreases in the anterior-posterior (dorsoventral) direction, which is consistent with the results of HRCT-based studies. This is because during the breathing movement, the chest wall movement mainly changes the anteroposterior diameter of the chest cavity.

[0114] Previous studies have reported increased diaphragmatic activity in patients with COPD at rest. In contrast, diaphragmatic movement during quiet breathing in patients with IPF is comparable to that in the healthy control group, but the amplitude of the area-time curve in the coronal and right sagittal planes of patients with IPF decreases, especially during deep breathing. By comparing the amplitude of the movement curves of the two groups of patients at rest and during deep breathing, the results show that the movement reserve capacity of the respiratory muscles in patients with IPF is significantly weakened.

[0115] The correlation between diaphragmatic movement and lung function has been verified in studies of healthy volunteers and patients with COPD. In patients with IPF, the diaphragmatic and chest wall movement function parameters on dynamic MRI during deep breathing are correlated with the predicted values of FVC%, FEV% and TLC%. At the same time, the increase in diaphragmatic curvature is accompanied by the decrease in TLV, FVC%, FEV% and TLC%, suggesting that the dysfunction of the diaphragm and chest wall in patients with IPF is related to lung dysfunction and mainly affects the pulmonary ventilation function of patients. And the predicted value of FVC% plays an important role in both clinical drug trials and the evaluation of disease progression, indicating that the parameters of chest wall and diaphragmatic movement and morphology measured by MRI are expected to become indicators for evaluating the disease severity and progression of patients with IPF.

[0116] Diaphragmatic weakness is related to respiratory symptoms, especially exercise intolerance, dyspnea, sleep disorders, and in the most severe cases, is associated with poor prognosis of the disease. Santana et al. suggested through diaphragmatic ultrasound that the diaphragmatic mobility decreases during deep breathing in patients with fibrotic ILD, and is correlated with increased dyspnea, reduced quality of life, and deteriorated lung function. The current results show that the reduction in diaphragmatic and chest wall movement is correlated with the reduction in 6MWD and severe dyspnea, suggesting that the deterioration of exercise tolerance and respiratory symptoms in patients with IPF may be accompanied by weakened movement function of the respiratory muscles.

[0117] Although the results of this example find no significant correlation between the diaphragmatic and chest wall movement function indexes and the degree of pulmonary fibrosis, there is a good correlation with the parameters of pulmonary vessels, including the volume, branch number, and curvature of the total pulmonary vessels, pulmonary arteries, and pulmonary veins. Previous quantitative CT studies have found that pulmonary vessel parameters, especially pulmonary vessel volume, are highly correlated with the disease severity and prognosis of patients. At the same time, the remodeling of pulmonary vessels also participates in the process of pulmonary fibrosis. Therefore, these results suggest that the decline in the movement function of the respiratory muscles in patients with IPF is related to the disease severity and prognosis.

[0118] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A method for evaluating the motor function of respiratory muscles in IPF patients based on dynamic MRI, characterized in that: The following steps are involved: (1) Determine the lung function parameters of the subject; (2) Performing a dynamic MRI scan on the subject to obtain dynamic MRI images of the lungs; (3) Manually mark and segment the end-expiratory and end-inspiratory images along the inner edge of the chest contour on the dynamic MRI images of the lungs, and perform inspection and correction; (4) using the above images to obtain evaluation parameters of chest wall motion and evaluation parameters of diaphragm motion and morphology; (5) Analyze the measured parameters and quantify the degree of lung fibrosis and pulmonary vascular and chest wall muscle parameters on HRCT images; (6) Compare and statistically analyze the parameters obtained from steps (1) to (5) of the different subjects to evaluate the respiratory muscle motor function of IPF patients.

2. The method for evaluating the respiratory muscle motor function of IPF patients based on dynamic MRI according to claim 1, characterized in that: In step (1), the lung function parameters include the percentage of the subject's forced expiratory volume in one second to the predicted value, the percentage of the forced vital capacity to the predicted value, the ratio of the forced expiratory volume in one second to the forced vital capacity, the percentage of the total vital capacity to the predicted value, and the percentage of the carbon monoxide diffusion rate to the predicted value.

3. The method for evaluating the respiratory muscle motor function of IPF patients based on dynamic MRI as claimed in claim 1, characterized in that: In step (2), the dynamic MRI scan is performed at three different levels, namely, the coronal plane, the right sagittal plane and the axial plane; the three axial planes are located at the level of the aortic arch, the level of the tracheal carina and the level of the right liver apex, respectively; the coronal plane is located at the coronal plane passing through the tracheal bifurcation, and the right sagittal plane is located at the level passing through the pulmonary apex and the right liver apex in the coronal plane.

4. The method for evaluating the respiratory muscle motor function of IPF patients based on dynamic MRI as claimed in claim 1, characterized in that: In step (3), the manually annotated reference point marks are marked along the inner edge of the thorax at the most ventral, most dorsal, most left and most right sides of the axial image; the coronal image is marked at the highest point of the lung apex and the top of the diaphragm; and the right sagittal image is marked at the lung apex and the front of the diaphragm, the top of the diaphragm and the back of the diaphragm.

5. The method for evaluating the respiratory muscle motor function of IPF patients based on dynamic MRI as claimed in claim 1, characterized in that: In step (4), the evaluation parameters of the chest wall movement include the anterior-posterior diameter, the left-right diameter and the chest cavity area on the axial image, and the evaluation parameters of the diaphragm movement and morphology include the cranio-caudal diameter on the coronal image, the area on the coronal image, the cranio-caudal diameter on the right sagittal image, the area on the sagittal image, and the height and area below the diaphragm.

6. The method for evaluating the respiratory muscle motor function of IPF patients based on dynamic MRI as claimed in claim 1, characterized in that: In step (5), the analysis and measurement parameters include: measuring all the end-expiratory and end-inspiratory diameter values ​​in 40 frames of images collected within 16 seconds of each phase of the MRI image, and then calculating the end-expiratory and end-inspiratory average values ​​respectively, and using the ratio between the end-inspiratory and end-expiratory average values ​​and the chest area ratio to represent the changing characteristic parameters of the chest and diaphragm movement; the pulmonary vascular related parameters include the total pulmonary vascular volume, pulmonary artery volume, pulmonary vein volume, the total number of pulmonary vascular branches, the number of pulmonary artery branches, the number of pulmonary vein branches, the total pulmonary vascular tortuosity, pulmonary artery tortuosity, pulmonary vein tortuosity, extrathoracic muscle volume, density and mass.

7. The method for evaluating the respiratory muscle motor function of IPF patients based on dynamic MRI according to claim 1, characterized in that: In step (6), during the statistical analysis, unpaired t-test and Mann-Whitney U test were used for continuous variables, Fisher's exact test or chi-square test was used for categorical variables, Spearman correlation coefficient was used to analyze the correlation between clinical indicators and MRI indicators, IBM SPSS 26.0 statistical analysis software was used for analysis, and GraphPad Prism 9.0 software was used for drawing. p ≤ 0.05 was considered to be statistically significant.

8. An application of the respiratory muscle motor function assessment result obtained by the method according to any one of claims 1 to 7 in determining the severity of IPF, characterized in that: Respiratory muscle motor function is correlated with TLV, FVC%, FEV%, TLC%, DLco%, 6-MWD, chest wall muscle volume and quality, and dyspnea symptoms. It is also correlated with the volume, number of branches, and tortuosity of the pulmonary vessels. The parameters used to evaluate the respiratory muscle motor function are correlated with the parameters for evaluating the severity of IPF.

9. The use according to claim 8, characterized in that The parameters of respiratory muscle motor function include MRI image parameters of chest wall and diaphragm movement, such as anteroposterior diameter, left-right diameter, cranio-caudal diameter and thoracic area ratio; the parameters for assessing the severity of IPF include TLV, FVC%, FEV%, TLC%, DLco%, 6-MWD, chest wall muscle volume and quality, dyspnea score, total pulmonary blood vessels, curvature, and the number of pulmonary artery and pulmonary vein branches.

10. The use according to claim 9, characterized in that The MRI image parameters of the chest wall and diaphragm movement, the anterior-posterior diameter, the left-right diameter, the cranio-caudal diameter and the thoracic area ratio, are positively correlated with the number of total pulmonary blood vessels, pulmonary arteries and pulmonary vein branches, and negatively correlated with the curvature.

Images