Abstract
Background:
Given the rarity of tracheobronchopathia osteochondroplastica (TO), many young doctors in primary hospitals are unable to identify TO based on bronchoscopy findings.
Objectives:
To build an artificial intelligence (AI) model for differentiating TO from other multinodular airway diseases by using bronchoscopic images.
Design:
We designed the study by comparing the imaging data of patients undergoing bronchoscopy from January 2010 to October 2022 by using EfficientNet. Bronchoscopic images of 21 patients with TO at Anhui Chest Hospital from October 2019 to October 2022 were collected for external validation.
Methods:
Bronchoscopic images of patients with multinodular airway lesions (including TO, amyloidosis, tumors, and inflammation) and without airway lesions in the First Affiliated Hospital of Guangzhou Medical University were collected. The images were randomized (4:1) into training and validation groups based on different diseases and utilized for deep learning by convolutional neural networks (CNNs).
Results:
We enrolled 201 patients with multinodular airway disease (38, 15, 75, and 73 patients with TO, amyloidosis, tumors, and inflammation, respectively) and 213 without any airway lesions. To find multinodular lesion images for deep learning, we utilized 2183 bronchoscopic images of multinodular lesions (including TO, amyloidosis, tumor, and inflammation) and compared them with images without any airway lesions (1733). The accuracy of multinodular lesion identification was 98.9%. Further, the accuracy of TO detection based on the bronchoscopic images of multinodular lesions was 89.2%. Regarding external validation (using images from 21 patients with TO), all patients could be diagnosed with TO; the accuracy was 89.8%.
Conclusion:
We built an AI model that could differentiate TO from other multinodular airway diseases (mainly amyloidosis, tumors, and inflammation) by using bronchoscopic images. The model could help young physicians identify this rare airway disease.
Introduction
Tracheobronchopathia osteochondroplastica (TO), a rare, benign disorder involving the lumen of the trachea-bronchial tree, is characterized by multiple cartilaginous and submucosal osseous nodules in the trachea and bronchus. As well as the TO nodules are located along the airway cartilage side but not along the posterior membranous wall of the large airways.1,2 The classical radiological features for TO are shown as follows. On the one hand, the thickness of the airway wall is increased. On the other hand, multiple calcified shadows can be found along the airway cartilage side but not along the posterior wall. However, computed tomography (CT) was unable to detect calcified nodules in the majority of TO patients. 3 Although TO is rare, there have been many reports in which it was occasionally diagnosed.1,4–27 To date, only a limited number of studies have utilized extensive data to conduct a comprehensive investigation of this disease.3,28
Nowadays, artificial intelligence (AI) has been used to assist physicians in better detecting lesions under gastrointestinal endoscopy and making a diagnosis.3,29–34 However, AI has not been frequently utilized to assist physicians by using bronchoscopy data, which has been reported to be used only for identifying between vocal cord and tracheal, as well as between the carina and main bronchi.35,36 Recently, Li et al. 37 conducted a study on using AI to recognize comprehensively anatomical positions by using bronchoscopy data.
TO could be asymptomatic or manifest in the form of common respiratory symptoms such as cough, sputum production, and dyspnea. Its diagnosis is based on bronchoscopy and pathology findings, and its treatment, in turn, is based on its diagnosis, for which a specific strategy is lacking. 38 In the past 10 years, the use of flexible bronchoscopy increased approximately five-fold in China. 39 However, given the rarity of TO, many young doctors in primary hospitals are unable to identify TO based on bronchoscopy findings. Because many young doctors in primary hospitals do not have chances to meet patients with TO. Even in some high-level hospitals, advanced respiratory doctors do not have chances to touch the bronchoscopes. Further, as one of the multinodular airway diseases, TO should also be distinguished from other airway diseases (including tumor, inflammation, and amyloidosis), and the sample figures of inflammation and tumor could find that they were difficult to differentiate (Supplemental Figures 1 and 2). Therefore, this deep learning-based study was aimed at building an AI model by using a convolutional neural network (CNN) to help young physicians identify TO from other multinodular airway diseases by using bronchoscopic images so as to avoid misdiagnoses.
Methods
Patients who were found to have diffuse and multinodular airway lesions under bronchoscopy and based on pathologic testing at the First Affiliated Hospital of Guangzhou Medical University from January 2010 to October 2022 were included. Bronchoscopic image data were used to distinguish between TO and other diffuse and multinodular airway diseases (such as amyloidosis, tumors, and inflammation). The sample bronchoscopic images of tumors and inflammation are shown in Supplemental Figures 1 and 2, respectively, which were extremely similar to those of TO. As a rare airway disease, amyloidosis is always discussed with TO, which is why we considered amyloidosis, tumors, and inflammation in the differential diagnosis of TO.
As a famous department for respiratory medicine in China, since 2009, the First Affiliated Hospital of Guangzhou Medical University has been the top respiratory medicine center in the country, with the average annual number of hospitalizations reaching 70,000 and the average number of outpatient visits reaching over 1,000,000. Therefore, data for many cases of rare diseases (such as TO and amyloidosis) could be collected. The data for external validation (patients with TO) were collected from Anhui Chest Hospital, a famous provincial hospital in China. The external validation dataset was collected by doctor FT from Anhui Chest Hospital, who was blinded to the process of internal AI model building and internal/external validating.
Five groups of participants were included in the study: patients with TO, amyloidosis, tumors, and inflammation, and healthy individuals. The bronchoscopic images of patients with multinodular diseases (TO, amyloidosis, tumors, and inflammation) were compared with those of individuals without any airway lesions. Second, the bronchoscopic images of patients with TO were compared with those of patients with other multinodular diseases (amyloidosis, tumors, and inflammation). Lastly, the external dataset of bronchoscopic images obtained for patients with TO was used for validation.
Inclusion and exclusion criteria
The inclusion criteria were as follows: (1) patients older than 14 years of age, (2) patients diagnosed with multinodular airway diseases based on bronchoscopic findings, (3) patients with multinodular airway disease with a pathological diagnosis of TO, amyloidosis, tumors, and inflammation, and (4) patients without any overlapping airway disease (such as overlapping TO and tumors or overlapping TO and inflammation). Patients without clear bronchoscopic image data (probably due to the date of examinations) were excluded.
The inclusion criteria for bronchoscopic images were as follows: (1) the scope of the lesions was more than one-third of the picture, (2) the scope of the blood was less than one-quarter of the picture, (3) the absence of any operative apparatus in the picture, (4) the absence of sputum in the picture, (5) and adequate image clarity. All images were selected by two independent investigators (CXC and FT), and duplicate or similar images were deleted. Finally, any differences in opinion between the first two investigators were resolved by a third investigator (SYL).
Statistical analysis
Categorical variables are expressed as numbers and percentages, and continuous variables are expressed as mean ± standard deviation. Python3.7 was used for AI analysis. EfficientNet (a CNN) was used for deep learning to differentiate TO from other diffusive nodular diseases (amyloidosis, tumor, and inflammation). The EfficientNet could ignore the influence of the pixel. 40 We also tried several different AI models (Inception, ResNet, VGG) to distinguish TO from other diseases before utilizing EfficientNet model. The sensitivity, specificity, positive predicted value (PPV), and negative predicted value (NPV) for finding TO by Inception model were 73.5%, 95.8%, 80.3%, and 93.9%, respectively (Supplemental Figure 3). Moreover, the sensitivity, specificity, PPV, and NPV for finding TO by ResNet were 79.5%, 97.5%, 88.0%, and 95.3%, respectively (Supplemental Figure 4). Lastly, the sensitivity, specificity, PPV, and NPV for finding TO by VGG were 85.5%, 97.2%, 87.7%, and 96.6%, respectively (Supplemental Figure 5). Image classification is one of the most basic jobs in pattern identification and computer vision; it translates obtainable features from the image into feature vectors that could be known by computers. 41 So, the method of CNNs was to figure out the features of the figures by computers, which could not be explained in detail. 41 The bronchoscopic images of all the airway anatomical positions were pre-processed using the Gaussian filter, graphic lightening, and normalizing. The confusion matrix and receiver operating characteristic curves (ROCs) were plotted for determining accuracy. The findings of this study adhere to the guidelines outlined in the Standards for Reporting of Diagnostic Accuracy (STARD) statement. 42
Results
We included 201 patients with diffuse and nodular airway disease: 38, 15, 75, and 73 patients were diagnosed with TO, amyloidosis, tumors, and inflammation, respectively, based on pathologic testing. Furthermore, 213 patients without any nodular lesions were included as a comparator group. For external validation, the Anhui Chest Hospital offered 177 bronchoscopic images of 21 patients with TO (Table 1).
The baseline characteristics of the enrolled patients and images.
TO, tracheobronchopathia osteochondroplastica.
Among the included patients with tumors, 22, 16, 5, 10, 8, and 5 patients were diagnosed with lung adenocarcinoma, lung squamous cell carcinoma, non-small-cell lung cancer (NSCLC, un-classified), small-cell lung cancer, metastatic carcinoma (of the breast, digestive tract, and thymus gland), and other types of tumor (such as big-cell lung cancer, lymphoma, lymphoepithelioma, esothelioma, and adenoid cystic carcinoma), respectively. The remaining nine patients were diagnosed as having cancer without classification via pathologic testing. Among the included patients with inflammation, 32, 6, and 35 were diagnosed with granulomatous inflammation, eosinophilic inflammation, and other types of common acute/chronic inflammation, respectively. The types of tumors and inflammation are shown in Table 2.
Classifications of inflammation and tumors included in the study.
The total number of the images used for training and validation from our hospital was 3916: the numbers of the bronchoscopic images of TO, amyloidosis, tumors, inflammation, and without any nodular lesions were 416, 370, 561, 836, and 1733, respectively. In every group, 80% of bronchoscopic images were randomly chosen as the training dataset, and the remaining 20% were chosen as the internal validation dataset (Table 1).
The included patients were divided into two groups: patients with multinodular airway disease and patients without any nodular airway disease. The model’s accuracy for recognizing the bronchoscopic images of multinodular lesions was 98.9% (Figure 1). Figure 2 shows the area under the ROC for recognizing multinodular airway lesions for the AI model; the results were both 0.999. The train and validation losses associated with the AI model for recognizing multinodular airway disease are shown in Figure 3.

The AI model’s accuracy in recognizing multinodular airway lesions.

The receiver operating characteristic curve for the recognition of multinodular airway lesions by the AI model.

The train and validation loss curves for multinodular airway lesion recognition by the AI model.
With regard to the identification of TO-related images from among the images of multinodular disease, the bronchoscopic images were classified into two groups: TO and non-TO. The bronchoscopic images for inflammation and tumors were added to the control group. The results showed that the sensitivity, specificity, PPV, and NPV were 89.2%, 97.5%, 89.2%, and 97.5%, respectively (Figure 4). Figure 5 shows an AUC of 0.986 for the recognition of TO from among other multinodular airway diseases. The train and validation losses of the AI model for recognizing TO from among the bronchoscopic images of multinodular diseases are shown in Figure 6.

The accuracy of TO recognition by the AI model.

The receiver operating characteristic curve of TO recognition by the AI model.

The train and validation loss curves for TO recognition by the AI model.
For external validation, 177 bronchoscopic images obtained from 21 patients with TO were used for validating the AI model (Table 1), and the accuracy for TO identification was 89.8%. Supplemental Figure 9 shows the sample bronchoscopic images chosen by the AI model as those corresponding to TO in the external dataset.
Discussion
Our AI study showed that the AI model could be used to recognize diffuse and multinodular airway disease by using bronchoscopy data. Moreover, the AI model trained by us could distinguish TO from other diffuse and nodular diseases (amyloidosis, inflammation, and tumor) with relatively high accuracy. 43
We also conducted three two-class image classifications (TO versus malignancy, TO versus amyloidosis, and TO versus inflammation). The sensitivity, specificity, PPV, and NPV of AI model for differentiating between TO and Malignancy were 92.8%, 97.3%, 96.3%, and 94.8%, respectively. (Supplemental Figure 6) The sensitivity, specificity, PPV, and NPV of AI model for differentiating between TO and amyloidosis were 97.6%, 98.6%, 98.8%, and 97.3%, respectively. (Supplemental Figure 7) The sensitivity, specificity, PPV, and NPV of the AI model for differentiating between TO and inflammation were 96.4%, 98.8%, 97.6%, and 98.2%, respectively. (Supplemental Figure 8).
The reasons for incorrect recognition are shown as follows. Firstly, the incidences of TO and amyloidosis were rare, as a two-center study, the enrolled number of patients was still small. Secondly, as one of the multinodular airway diseases, TO should also be distinguished from other multinodular airway diseases (tumor, inflammation, or amyloidosis). The sample figures of inflammation and tumor we proposed could find that they were difficult to differentiate (Supplemental Figures 1 and Figure 2).
TO is a rare disease characterized by diffuse nodular airway lesions, and related tissue compositions are mainly calcareous. Many theories about TO pathogenesis have been proposed; however, the exact cause of the disease remains unknown. These theories include chronic airway inflammation, a congenital basis, chemical or mechanical irritation, metabolic disturbance, degenerative processes, ecchondrosis/exostosis, and metaplasia of elastic tissue. A recent study by Hong et al. 38 demonstrated that dysfunction of airway basal stem cells is a significant factor in the pathophysiology of TO. In our view, The AI model probably recognized patients with these conditions based on bronchoscopic images by recognizing the distribution and color characteristics of nodules. However, this is only our presumption, and the precise underlying disease mechanism remains unknown.
Many associations between TO and other clinical conditions have been described. Hence, caution should be exercised in the evaluation of TO since it could co-exist with sarcoidosis, tumors, and amyloidosis.44,45 We excluded three patients with TO and tumors (lung adenocarcinoma, lung squamous cell carcinoma, and malignant fibroma). While bronchoscopy can be used to diagnose TO, biopsy is essential for excluding other potential causes. 28 This is why our research focused on obtaining a pathological diagnosis. In the inflammation group, we comprehensively considered disorders including tuberculosis, 46 and sarcoidosis. 47 The tumor group included patients such as those with lung cancer, breast cancer, and lymphoma. 48
We previously used an AI model to differentiate nine anatomical positions in the airway based on bronchoscopy data. 49 In our view, various backgrounds of bronchoscopy (many bronchi and lobes) could bring problems to the AI study. The lesions of multinodular airway disease in our study were mainly located in the trachea and main bronchi (large airways). The use of images of diffuse and multinodular airway disease for differential diagnosis could address the problems posed by various background factors. Because multinodular lesions were widely distributed in the airway, we did not annotate the lesions on the images.
Up to now, many AI-associated studies about pulmonary diseases have shown up. These previous studies used AI for managing lung cancer, 50 chronic obstructive pulmonary disease (COPD),51–53 infectious pulmonary diseases,54,55 and acute respiratory distress syndrome. 56 However, most of them were analyzed by using CT, and ultrasound.57,58 And there were few studies using bronchoscopic images for AI study.
After the supervised machine learning, the training model could classify the images that could promptly and automatically collect image data during examination. The algorithm research of CNN went through ALexNet, 59 VGG, 60 ResNet, 61 and EfficientNet. 40 Now, the EfficientNet added the attention mechanism with high efficiency, and could ignore the influence of pixel. 40
The limitations of this study were as follows. Firstly, we only included 38 patients with TO for training and testing from our hospital, and the AI model trained was mainly aimed at differentiating TO. The accuracy of tumor and inflammation detection was limited because of the varying types of tumors (including lung adenocarcinoma, lung squamous cell carcinoma, and small-cell lung cancer) and inflammation (including due to granuloma, fungal infection, and tuberculosis) present. In the future, we could include more bronchoscopic images from patients with tumors or inflammation to differentiate patients (for subgroup analysis). Secondly, image inclusion and exclusion were mainly based on the pathophysiological characteristics of the multinodular disease (such as the size of the lesions). Thirdly, this study only included two centers with Chinese patients; future studies should include larger populations with a variety of patients. However, although our study only included 59 patients because of the rarity of TO, it was still the largest population of patients with TO discussed thus far. Lastly, we did not calculate the sample size selected in this study.
In the future, AI could be a teaching tool for young doctors in primary hospitals. We hope to conduct a worldwide multi-center study based on bronchoscopy image data, which could help us increase the effects of AI.
Conclusion
The AI model trained by us could distinguish between TO and other multinodular diseases caused by tumors or inflammation. Thus, it can be used to help teach young physicians and remote clinical workers to recognize this rare disease by using bronchoscopy data.
Supplemental Material
sj-doc-1-tar-10.1177_17534666241253694 – Supplemental material for Building and validating an artificial intelligence model to identify tracheobronchopathia osteochondroplastica by using bronchoscopic images
Supplemental material, sj-doc-1-tar-10.1177_17534666241253694 for Building and validating an artificial intelligence model to identify tracheobronchopathia osteochondroplastica by using bronchoscopic images by Chongxiang Chen, Fei Tang, Felix J. F. Herth, Yingnan Zuo, Jiangtao Ren, Shuaiqi Zhang, Wenhua Jian, Chunli Tang and Shiyue Li in Therapeutic Advances in Respiratory Disease
Supplemental Material
sj-docx-2-tar-10.1177_17534666241253694 – Supplemental material for Building and validating an artificial intelligence model to identify tracheobronchopathia osteochondroplastica by using bronchoscopic images
Supplemental material, sj-docx-2-tar-10.1177_17534666241253694 for Building and validating an artificial intelligence model to identify tracheobronchopathia osteochondroplastica by using bronchoscopic images by Chongxiang Chen, Fei Tang, Felix J. F. Herth, Yingnan Zuo, Jiangtao Ren, Shuaiqi Zhang, Wenhua Jian, Chunli Tang and Shiyue Li in Therapeutic Advances in Respiratory Disease
Footnotes
References
Supplementary Material
Please find the following supplemental material available below.
For Open Access articles published under a Creative Commons License, all supplemental material carries the same license as the article it is associated with.
For non-Open Access articles published, all supplemental material carries a non-exclusive license, and permission requests for re-use of supplemental material or any part of supplemental material shall be sent directly to the copyright owner as specified in the copyright notice associated with the article.
