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Experimental research and modeling of selected layers of the trachea based on EBUS

Experimental research and modeling of selected layers of the trachea based on EBUS This study presents the use of endobronchial ultrasound (EBUS) for imaging and dimensional measurements of a trachea. An assessment of shape reproduction accuracy was based on a comparative method using oneand two-later models. It was found that dimensions determined from EBUS scans of digital models are overstated by 1.2­2.9 mm on average. Developed 2-D and 3-D models of tracheal structures facilitate the evaluation of dimensions and thickness distribution for tissue layers. Keywords: biomeasurements; ultrasound. modeling; trachea; roduction Normal pulmonary function and appropriate oxygen exchange belong to essential processes in a human body. Their performance depends on numerous factors, including the tracheal lumen. Changes in the tracheal structure are observed in chronic obstructive pulmonary disease (COPD) and bronchial asthma [1]. Basic differences concern the thickening of the basement membrane and mucous glands hypertrophy. Successive stages of the bronchial wall remodeling, including epithelial damage, increased smooth muscles mass resulting from hypertrophy and hyperplasia, angiogenesis, and proteoglycans and elastin deposition, are significantly less pronounced in COPD than in asthma [2­5]. *Corresponding author: Lukasz Bojko, Faculty of Mechanical Engineering and Robotics, AGH The University of Science and Technology, Al. Mickiewicz 30, Kraków 30-059, Poland, E-mail: lbojko@op.pl. http://orcid.org/0000-0002-6024-458X Andrzej Ryniewicz: Laboratory of Coordinate Metrology, Faculty of Mechanical, Cracow University of Technology, Krakow, Poland Jerzy Soja and Krzysztof Sladek: Faculty of Medicine, II Department of ernal, Jagiellonian University Medical College, Krakow, Poland Wojciech Ryniewicz: Faculty of Medicine, Department of Prosthodontics, Jagiellonian University Medical College, Krakow, Poland. http://orcid.org/0000-0003-3564-2321 Endobronchial ultrasound (EBUS) is a noninvasive method facilitating imaging of airways, lung parenchyma, and structures located in the mediastinum. First attempts to use this method were made in the early 1990s and are associated with the development of a rotating ultrasound probe. Usually, distinguishing of mediastinal structures during EBUS poses significant problems resulting from motion artifacts and diagonal cross-sectional planes related to the airways shape [6]. Further dimensional orientation is supported by imagining the esophagus, facilitating positioning of the tracheal posterior wall and the left primary bronchus. With beam penetration of 2­3 cm, pulmonary trunk division, right and left pulmonary arteries, the superior vena cava, the aortic root, the ascending aorta, the aortic arch, and the aortopulmonary window can be shown (Figure 1). The most common indications for EBUS include progression assessment for non-small-cell lung carcinoma. Attempts are also made to use EBUS in diagnostic evaluation of early stages of the lung cancer, erventional pulmonology, and diagnosis of peripheral lesions [7]. Endoscopic methods, such as endoscopic ultrasound (EUS) and EBUS, and imaging methods, including computed tomography of the chest and positron emission tomography, play increasingly important role in lung cancer staging (Figure 2) [8­10]. Diagnosing airway peripheral lesions often represents a significant clinical problem, particularly when the size of lesions does not exceed 20 mm. So far, they have been investigated by an ultrasound-guided needle biopsy through the chest wall or by a fluoroscopy-guided transbronchial biopsy performed during bronchofiberoscopy [11, 12]. Currently, an EBUS procedure with miniature probes seems to be very promising. Peripheral lesions are usually clearly delimited because of a strong echo between the aerated lung parenchyma and the lesion [13]. EBUS-guided biopsies of peripheral lesions contributed to the increased diagnostic effectiveness of this method, particularly for lesions invisible in standard bronchofiberoscopy. In some cases, EBUS allowed distinguishing between peripheral lesions according to their nature [14­16]. 218Ryniewicz et al.: Experimental research and modeling of the trachea based on EBUS Figure 1:Airway images: (A) diagonal cross-sectional planes and (B) branching of the left and the right bronchi. Materials and methods Study objective The aim of this study was to assess the reconstruction accuracy of the tracheal shape and its layered wall structure on a basis of diagnostic EBUS using numerical modeling and reference templates. Study material and methods Figure 2:Lung cancer imaging. The process of bronchial wall remodeling involves numerous structural changes. The most commonly known changes include the thickening of the basement membrane caused by collagen, fibronectin and tenascin deposits, an increased number of myofibroblasts, smooth muscles hypertrophy and hyperplasia, vascular and nerve proliferation, and hypertrophy of mucous glands and goblet cells. A three-dimensional reconstruction of images acquired during the scan also appears eresting. Andreassen et al. [17], in their studies involving use of a balloon-tipped probe, showed that such reconstruction improved visualization of bronchial wall layers. Problems with ultrasound imagining resulted from a short distance between a transducer and a bronchial wall evaluated by EBUS, a small wall thickness, and from a need to visualize its layered structure [18]. However, the main problem was the accuracy of tracheal size and shape reconstruction in the EBUS-based numerical modeling. Study material consisted of the following: ­ EBUS diagnostic imaging of the trachea in bronchial asthma patients ­ Imaging of one- and two-layer reference models of trachea using the same parameters as imagining in patients Tracheas of 20 patients (age 45­60 years) were imagined in their middle section, before their branching o the right and left bronchi. To determine the accuracy of shape reconstruction, four one- and two-layer reference models were proposed, constructed of materials of acoustic properties similar to tracheal tissues (Figure 3). The EBUS method was used in clinical and comparative studies. The scans were performed at the Laboratory for Invasive Diagnostic of Chest Diseases, 2nd ernal Medicine Chair, Jagiellonian University Medical College, under local anesthesia, using the bronchoscopy diagnostic system, model Evis Exera II CLV-180 (Olympus, Tokyo, Japan) provided with a high-definition image processing function, a narrow band imaging technology, and a function for digital recording of stationary and moving images [19]. Spatial resolution was 0.1 mm×0.1 mm×1.5 mm. The field of vision used in the study was 60 mm×60 mm, and Ryniewicz et al.: Experimental research and modeling of the trachea based on EBUS219 Figure 3:Reference models for accuracy assessment for EBUS system imaging. Figure 4:Bronchoscopy system Evis Exera II CLV-180 (Olympus). the pixel size was 0.13 mm×0.13 mm. With an image zoom in option, layer edges were determined with subpixel precision. The acquired signal was displayed in a real time on a screen from the same company. The diagnostic system was connected with a miniature Olympus probe (Figure 4) of 2.8 mm in diameter, compatible with the UM-BS20-26R processor working in the working channel of the bronchofiberscope, with a dedicated disposable septic balloon MAJ-643R. The used probe was of a radial type, with a 360° scanning sector and a 20-MHz working frequency (optimal for bronchial scans). The 20-MHz radial probe (Figure 5) was used for mediastinum imaging. Before imaging was started, the probe was filled with distilled water. The balloon surrounding the probe and tightly adhering to the bronchial wall allowed acquiring of ultrasound images eliminating artifacts resulting from presence of air in airways, as well as the precise assessment of the bronchial wall and its surrounding structures. With the EBUS system, five layers can be distinguished in the bronchial wall. In the diagnostics and therapy of bronchial asthma and COPD, the structure of the first and the second layers consisting of mucosa, submucosa, and smooth muscles is of importance. Therefore, in a procedure for distinguishing structures according to preset thresholds, surfaces of the first and the second layers were selectively considered. The segmentation procedure of the Amira 5.2.2. application (Visualization Sciences Group, Bordeaux, France and the Zuse Institute Berlin (ZIB), Germany) allowed determining layer contours, establishing selectively diagnosed areas in successive planes, measurements according to the adapted measuring strategy, and finally the 3-D reconstruction. For each patient, 20 measurements of ernal diameters and their statistical analysis were performed. Then the digital control pipe models determined with the EBUS procedure were compared to the reference models. The reference models were established in coordinate studies. The best fit method was used to analyze results in a Geomagic Qualify application (3D Systems, Rock Hill, SC, USA). In the shape comparison procedure, it automatically aligns compared bodies and then identifies positive and negative deviations resulting from the reconstruction accuracy of an EBUS model shape versus the reference model. Results When patients were diagnosed, results were shown as digital images obtained from the ultrasound probe, which Figure 5:The 20-MHz ultrasound probe (A) radial probe and (B) probe with a balloon sheath. 220Ryniewicz et al.: Experimental research and modeling of the trachea based on EBUS 20 Diameter, mm 15 Range The minimum diameter Tube I Tube II Tube III Tube IV Figure 7:Measurements results and their range for ernal and ernal diameter measurements in reference models using an optical microscope. Figure 6:Determination of the first tracheal layer on a basis of EBUS clinical scans. then were segmented using thresholding with hysteresis and digitally analyzed (Figure 6). Areas corresponding to specific layers of tracheal tissues were designated, with upper and lower thresholds defined on a gray scale. In this procedure, an isosurface of the first layer was determined, bounded on the inside by an edge of a contact zone of the trachea and the radial probe with a balloon sheath (grayscale threshold 55­66) and on the outside by the edge consisting of mucosa, submucosa, and smooth muscles (grayscale threshold 79­83). Curves limiting selected areas were generated. The Dice's coefficient was 0.72. Then the spatial reconstruction was performed, combining 2-D models and generating a body reflecting a structure of the trachea. Examples of results for selected four measurement series for the patient IX are provided in Table 1. Results of reference diameter measurements for standard models, that is, two-layer ­ model No. 1 and one-layer ­ mode No. 2, are shown in Figure 7. An example of an image for reference model measurements is shown in Figure 8. The conducted clinical studies combined with numerical procedures in the Amira 5.2.2. application allowed the reconstruction and visualization of studied tracheal sections. Figure 8:An image of an ernal diameter of a reference model based on EBUS. Discussion An analysis of results of ernal tracheal diameter measurements conducted in patients using the EBUS diagnostic system showed that the results deviation ranged from 10% to 32% versus the mean value of the measured diameter. Figure 9 shows mean diameters and a standard deviation for two reference models and three selected patients, Table 1:Examples of results for selected four series of ernal tracheal diameter measurements in patient IX. The measurement 1 2 3 4 The arithmetic mean, mm 17.97 17.70 17.79 18.16 Standard deviation, mm 0.09 0.11 0.22 0.07 The standard deviation of the mean, mm 0.02 0.02 0.05 0.02 Ryniewicz et al.: Experimental research and modeling of the trachea based on EBUS221 Diameter, mm The arithmetic mean Standard deviation ×10 Figure 11:Three-dimensional reconstruction of the first and the second tracheal layers in patient IX: (A) outside and (B) inside. Model I Model III Patient I Patient II Patient III Figure 9:Measurements results and standard deviations for reference models (one- and two-layer) and for three selected patients, based on EBUS imagining. 1.5 1 0.5 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Patient Figure 10:A change in a standard deviation for an experimental diameter measurement in 20 patients. were conducted with an optical microscope, with MPE for length measurements of 0.04 mm and MPE for shape measurements of 0.5 mm. Scans allowed thickness measurements for the first and the second layers and surface measurements for selected cross sections perpendicular to the tracheal axis. By contrast, in the 3-D configuration, they allowed determining bronchial wall deformation (remodeling), characteristic for bronchial asthma and COPD (Figure 11) [19]. The measurement procedures and the assessment of reconstruction errors can be used to determine the effectiveness of pharmacological therapy and in bronchial thermoplasty procedures. Experimental standard deviations, mm and Figure 10 shows changes in a standard deviation for diameter measurements for the studied patients. An accuracy of shape and size reproduction in EBUS was established by comparing reference dimensions with results of reference models imaging. It was found that mean values for measurement results for reference models diagnosed with the EBUS system are overstated by 1.2­2.9 mm, depending on the diameter of the measured standard. On a basis of conducted comparative measurements, it can be said that systematic errors occur, which should be corrected. Table 2 presents a comparison of measurements for standard models performed with the EBUS system versus the reference values. Measurements Conclusions 1. Numerical modeling based on EBUS can be used for evaluation of a shape and determining a layered structure of the tracheal wall. 2. The accuracy assessment using a comparative method and reference standards is a useful tool supporting the diagnostic procedure in EBUS. 3. Systematic errors were found for the conducted measurements, depending on a value of a measured parameter, as well as errors related to a central position of the measuring probe in the tracheal lumen. 4. The developed numerical models reconstructing the shape of the trachea and thickness of layers in its Table 2:Comparison of mean results for the ernal diameter measurements in reference models using an optical microscope versus the EBUS diagnostic system. The reference model No. 1 No. 2 No. 3 No. 4 The arithmetic mean of the measurements of microscopic, mm 16.14 9.80 6.18 19.02 The arithmetic mean of the measurements of EBUS, mm 18.23 12.73 9.05 20.25 The minimum value of the measurement system EBUS, mm 17.76 10.99 8.29 19.78 The maximum value of the measurement system EBUS, mm 19.03 13.42 9.80 21.91 222Ryniewicz et al.: Experimental research and modeling of the trachea based on EBUS walls are essential for a correct diagnosis and treatment of respiratory diseases. Author contributions: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission. Research funding: None declared. Employment or leadership: None declared. Honorarium: None declared. Competing erests: The funding organization(s) played no role in the study design; in the collection, analysis, and erpretation of data; in the writing of the report; or in the decision to submit the report for publication. in 150 patients with suspected lung cancer. Chest 2010;138: 790­4. Mikos M, Grzanka P, Sladek K, Pulka G, Bochenek G, Soja J, et al. High-resolution computed tomography evaluation of peripheral airways in asthma patients: comparison of focal and diffuse air trapping. Respiration 2009;77:381­8. Gomez M, Silvestri GA. Endobronchial ultrasound for the diagnosis and staging of lung cancer. Proc Am Thorac Soc 2009;6:180­6. Sammartino F. Macchiarini P. Primary tracheal tumors. Lung cancer, 4th ed. 2014:267­77. Szlubowski A, Kudal J, Kolodziej M, Soja J, Pankowski J, Obrochta A, et al. Endobronchial ultrasound-guided needle aspiration in the non-small cell lung cancer staging. Eur J Cardiothorac Surg 2009;35:332­5. Szlubowski A, Zieliski M, Soja J, Annema JT, Sonicki W, Jakubiak M, et al. A combined approach of endobronchial and endoscopic ultrasound-guided needle aspiration in the radiologically normal mediastinum in non-small-cell lung cancer staging ­ a prospective trial. Eur J Cardiothorac Surg 2010;37:1175­9. Aydogmus MT, Erkalp K, Sinikoglu SN, Usta TA, Ulger GO, Alagol A. Is ultrasonic investigation of transverse tracheal air shadow diameter reasonable for evaluation of difficult airway in pregnant women: a prospective comparative study. Pakistan J Med Sci 2014;30:91. Lie CH, Chao TY, Chung YH, Wang JL, Wang YH, Lin MC. New image characteristics in endobronchial ultrasonography for differentiating peripheral pulmonary lesions. Ultrasound Med Biol 2009;35:376­81. Agarwal A, Singh DK. Bronchoscopic topical steroid instillation in prevention of tracheal stenosis. J Anaesthesiol Clin Pharmacol 2014;30:91. Kang Y, Lee YK, Lee HS, Chae YK, Min J. Tracheal injury as a perforation of a newly formed tracheal diverticulum after tracheal ubation: a case report. Anesth Pain Med 2015;10:32­5. Andreassen AH, Ellingsen I, Nesje LB, Gravdal K, Ødegaard S. 3-D endobronchial ultrasonography ­ a post mortem study. Ultrasound Med Biol 2005;31:473­6. Purcell P, Meyer T, Allen C. Tracheal mass. JAMA Otolaryngol Head Neck Surg. 2015;141:291­2. Soja J, editors. Practical medicine, Krakow: the use of endobronchial ultrasound in the evaluation of remodeling in asthma, 2011. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Bio-Algorithms and Med-Systems de Gruyter

Experimental research and modeling of selected layers of the trachea based on EBUS

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de Gruyter
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Abstract

This study presents the use of endobronchial ultrasound (EBUS) for imaging and dimensional measurements of a trachea. An assessment of shape reproduction accuracy was based on a comparative method using oneand two-later models. It was found that dimensions determined from EBUS scans of digital models are overstated by 1.2­2.9 mm on average. Developed 2-D and 3-D models of tracheal structures facilitate the evaluation of dimensions and thickness distribution for tissue layers. Keywords: biomeasurements; ultrasound. modeling; trachea; roduction Normal pulmonary function and appropriate oxygen exchange belong to essential processes in a human body. Their performance depends on numerous factors, including the tracheal lumen. Changes in the tracheal structure are observed in chronic obstructive pulmonary disease (COPD) and bronchial asthma [1]. Basic differences concern the thickening of the basement membrane and mucous glands hypertrophy. Successive stages of the bronchial wall remodeling, including epithelial damage, increased smooth muscles mass resulting from hypertrophy and hyperplasia, angiogenesis, and proteoglycans and elastin deposition, are significantly less pronounced in COPD than in asthma [2­5]. *Corresponding author: Lukasz Bojko, Faculty of Mechanical Engineering and Robotics, AGH The University of Science and Technology, Al. Mickiewicz 30, Kraków 30-059, Poland, E-mail: lbojko@op.pl. http://orcid.org/0000-0002-6024-458X Andrzej Ryniewicz: Laboratory of Coordinate Metrology, Faculty of Mechanical, Cracow University of Technology, Krakow, Poland Jerzy Soja and Krzysztof Sladek: Faculty of Medicine, II Department of ernal, Jagiellonian University Medical College, Krakow, Poland Wojciech Ryniewicz: Faculty of Medicine, Department of Prosthodontics, Jagiellonian University Medical College, Krakow, Poland. http://orcid.org/0000-0003-3564-2321 Endobronchial ultrasound (EBUS) is a noninvasive method facilitating imaging of airways, lung parenchyma, and structures located in the mediastinum. First attempts to use this method were made in the early 1990s and are associated with the development of a rotating ultrasound probe. Usually, distinguishing of mediastinal structures during EBUS poses significant problems resulting from motion artifacts and diagonal cross-sectional planes related to the airways shape [6]. Further dimensional orientation is supported by imagining the esophagus, facilitating positioning of the tracheal posterior wall and the left primary bronchus. With beam penetration of 2­3 cm, pulmonary trunk division, right and left pulmonary arteries, the superior vena cava, the aortic root, the ascending aorta, the aortic arch, and the aortopulmonary window can be shown (Figure 1). The most common indications for EBUS include progression assessment for non-small-cell lung carcinoma. Attempts are also made to use EBUS in diagnostic evaluation of early stages of the lung cancer, erventional pulmonology, and diagnosis of peripheral lesions [7]. Endoscopic methods, such as endoscopic ultrasound (EUS) and EBUS, and imaging methods, including computed tomography of the chest and positron emission tomography, play increasingly important role in lung cancer staging (Figure 2) [8­10]. Diagnosing airway peripheral lesions often represents a significant clinical problem, particularly when the size of lesions does not exceed 20 mm. So far, they have been investigated by an ultrasound-guided needle biopsy through the chest wall or by a fluoroscopy-guided transbronchial biopsy performed during bronchofiberoscopy [11, 12]. Currently, an EBUS procedure with miniature probes seems to be very promising. Peripheral lesions are usually clearly delimited because of a strong echo between the aerated lung parenchyma and the lesion [13]. EBUS-guided biopsies of peripheral lesions contributed to the increased diagnostic effectiveness of this method, particularly for lesions invisible in standard bronchofiberoscopy. In some cases, EBUS allowed distinguishing between peripheral lesions according to their nature [14­16]. 218Ryniewicz et al.: Experimental research and modeling of the trachea based on EBUS Figure 1:Airway images: (A) diagonal cross-sectional planes and (B) branching of the left and the right bronchi. Materials and methods Study objective The aim of this study was to assess the reconstruction accuracy of the tracheal shape and its layered wall structure on a basis of diagnostic EBUS using numerical modeling and reference templates. Study material and methods Figure 2:Lung cancer imaging. The process of bronchial wall remodeling involves numerous structural changes. The most commonly known changes include the thickening of the basement membrane caused by collagen, fibronectin and tenascin deposits, an increased number of myofibroblasts, smooth muscles hypertrophy and hyperplasia, vascular and nerve proliferation, and hypertrophy of mucous glands and goblet cells. A three-dimensional reconstruction of images acquired during the scan also appears eresting. Andreassen et al. [17], in their studies involving use of a balloon-tipped probe, showed that such reconstruction improved visualization of bronchial wall layers. Problems with ultrasound imagining resulted from a short distance between a transducer and a bronchial wall evaluated by EBUS, a small wall thickness, and from a need to visualize its layered structure [18]. However, the main problem was the accuracy of tracheal size and shape reconstruction in the EBUS-based numerical modeling. Study material consisted of the following: ­ EBUS diagnostic imaging of the trachea in bronchial asthma patients ­ Imaging of one- and two-layer reference models of trachea using the same parameters as imagining in patients Tracheas of 20 patients (age 45­60 years) were imagined in their middle section, before their branching o the right and left bronchi. To determine the accuracy of shape reconstruction, four one- and two-layer reference models were proposed, constructed of materials of acoustic properties similar to tracheal tissues (Figure 3). The EBUS method was used in clinical and comparative studies. The scans were performed at the Laboratory for Invasive Diagnostic of Chest Diseases, 2nd ernal Medicine Chair, Jagiellonian University Medical College, under local anesthesia, using the bronchoscopy diagnostic system, model Evis Exera II CLV-180 (Olympus, Tokyo, Japan) provided with a high-definition image processing function, a narrow band imaging technology, and a function for digital recording of stationary and moving images [19]. Spatial resolution was 0.1 mm×0.1 mm×1.5 mm. The field of vision used in the study was 60 mm×60 mm, and Ryniewicz et al.: Experimental research and modeling of the trachea based on EBUS219 Figure 3:Reference models for accuracy assessment for EBUS system imaging. Figure 4:Bronchoscopy system Evis Exera II CLV-180 (Olympus). the pixel size was 0.13 mm×0.13 mm. With an image zoom in option, layer edges were determined with subpixel precision. The acquired signal was displayed in a real time on a screen from the same company. The diagnostic system was connected with a miniature Olympus probe (Figure 4) of 2.8 mm in diameter, compatible with the UM-BS20-26R processor working in the working channel of the bronchofiberscope, with a dedicated disposable septic balloon MAJ-643R. The used probe was of a radial type, with a 360° scanning sector and a 20-MHz working frequency (optimal for bronchial scans). The 20-MHz radial probe (Figure 5) was used for mediastinum imaging. Before imaging was started, the probe was filled with distilled water. The balloon surrounding the probe and tightly adhering to the bronchial wall allowed acquiring of ultrasound images eliminating artifacts resulting from presence of air in airways, as well as the precise assessment of the bronchial wall and its surrounding structures. With the EBUS system, five layers can be distinguished in the bronchial wall. In the diagnostics and therapy of bronchial asthma and COPD, the structure of the first and the second layers consisting of mucosa, submucosa, and smooth muscles is of importance. Therefore, in a procedure for distinguishing structures according to preset thresholds, surfaces of the first and the second layers were selectively considered. The segmentation procedure of the Amira 5.2.2. application (Visualization Sciences Group, Bordeaux, France and the Zuse Institute Berlin (ZIB), Germany) allowed determining layer contours, establishing selectively diagnosed areas in successive planes, measurements according to the adapted measuring strategy, and finally the 3-D reconstruction. For each patient, 20 measurements of ernal diameters and their statistical analysis were performed. Then the digital control pipe models determined with the EBUS procedure were compared to the reference models. The reference models were established in coordinate studies. The best fit method was used to analyze results in a Geomagic Qualify application (3D Systems, Rock Hill, SC, USA). In the shape comparison procedure, it automatically aligns compared bodies and then identifies positive and negative deviations resulting from the reconstruction accuracy of an EBUS model shape versus the reference model. Results When patients were diagnosed, results were shown as digital images obtained from the ultrasound probe, which Figure 5:The 20-MHz ultrasound probe (A) radial probe and (B) probe with a balloon sheath. 220Ryniewicz et al.: Experimental research and modeling of the trachea based on EBUS 20 Diameter, mm 15 Range The minimum diameter Tube I Tube II Tube III Tube IV Figure 7:Measurements results and their range for ernal and ernal diameter measurements in reference models using an optical microscope. Figure 6:Determination of the first tracheal layer on a basis of EBUS clinical scans. then were segmented using thresholding with hysteresis and digitally analyzed (Figure 6). Areas corresponding to specific layers of tracheal tissues were designated, with upper and lower thresholds defined on a gray scale. In this procedure, an isosurface of the first layer was determined, bounded on the inside by an edge of a contact zone of the trachea and the radial probe with a balloon sheath (grayscale threshold 55­66) and on the outside by the edge consisting of mucosa, submucosa, and smooth muscles (grayscale threshold 79­83). Curves limiting selected areas were generated. The Dice's coefficient was 0.72. Then the spatial reconstruction was performed, combining 2-D models and generating a body reflecting a structure of the trachea. Examples of results for selected four measurement series for the patient IX are provided in Table 1. Results of reference diameter measurements for standard models, that is, two-layer ­ model No. 1 and one-layer ­ mode No. 2, are shown in Figure 7. An example of an image for reference model measurements is shown in Figure 8. The conducted clinical studies combined with numerical procedures in the Amira 5.2.2. application allowed the reconstruction and visualization of studied tracheal sections. Figure 8:An image of an ernal diameter of a reference model based on EBUS. Discussion An analysis of results of ernal tracheal diameter measurements conducted in patients using the EBUS diagnostic system showed that the results deviation ranged from 10% to 32% versus the mean value of the measured diameter. Figure 9 shows mean diameters and a standard deviation for two reference models and three selected patients, Table 1:Examples of results for selected four series of ernal tracheal diameter measurements in patient IX. The measurement 1 2 3 4 The arithmetic mean, mm 17.97 17.70 17.79 18.16 Standard deviation, mm 0.09 0.11 0.22 0.07 The standard deviation of the mean, mm 0.02 0.02 0.05 0.02 Ryniewicz et al.: Experimental research and modeling of the trachea based on EBUS221 Diameter, mm The arithmetic mean Standard deviation ×10 Figure 11:Three-dimensional reconstruction of the first and the second tracheal layers in patient IX: (A) outside and (B) inside. Model I Model III Patient I Patient II Patient III Figure 9:Measurements results and standard deviations for reference models (one- and two-layer) and for three selected patients, based on EBUS imagining. 1.5 1 0.5 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Patient Figure 10:A change in a standard deviation for an experimental diameter measurement in 20 patients. were conducted with an optical microscope, with MPE for length measurements of 0.04 mm and MPE for shape measurements of 0.5 mm. Scans allowed thickness measurements for the first and the second layers and surface measurements for selected cross sections perpendicular to the tracheal axis. By contrast, in the 3-D configuration, they allowed determining bronchial wall deformation (remodeling), characteristic for bronchial asthma and COPD (Figure 11) [19]. The measurement procedures and the assessment of reconstruction errors can be used to determine the effectiveness of pharmacological therapy and in bronchial thermoplasty procedures. Experimental standard deviations, mm and Figure 10 shows changes in a standard deviation for diameter measurements for the studied patients. An accuracy of shape and size reproduction in EBUS was established by comparing reference dimensions with results of reference models imaging. It was found that mean values for measurement results for reference models diagnosed with the EBUS system are overstated by 1.2­2.9 mm, depending on the diameter of the measured standard. On a basis of conducted comparative measurements, it can be said that systematic errors occur, which should be corrected. Table 2 presents a comparison of measurements for standard models performed with the EBUS system versus the reference values. Measurements Conclusions 1. Numerical modeling based on EBUS can be used for evaluation of a shape and determining a layered structure of the tracheal wall. 2. The accuracy assessment using a comparative method and reference standards is a useful tool supporting the diagnostic procedure in EBUS. 3. Systematic errors were found for the conducted measurements, depending on a value of a measured parameter, as well as errors related to a central position of the measuring probe in the tracheal lumen. 4. The developed numerical models reconstructing the shape of the trachea and thickness of layers in its Table 2:Comparison of mean results for the ernal diameter measurements in reference models using an optical microscope versus the EBUS diagnostic system. The reference model No. 1 No. 2 No. 3 No. 4 The arithmetic mean of the measurements of microscopic, mm 16.14 9.80 6.18 19.02 The arithmetic mean of the measurements of EBUS, mm 18.23 12.73 9.05 20.25 The minimum value of the measurement system EBUS, mm 17.76 10.99 8.29 19.78 The maximum value of the measurement system EBUS, mm 19.03 13.42 9.80 21.91 222Ryniewicz et al.: Experimental research and modeling of the trachea based on EBUS walls are essential for a correct diagnosis and treatment of respiratory diseases. Author contributions: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission. Research funding: None declared. Employment or leadership: None declared. Honorarium: None declared. Competing erests: The funding organization(s) played no role in the study design; in the collection, analysis, and erpretation of data; in the writing of the report; or in the decision to submit the report for publication. in 150 patients with suspected lung cancer. Chest 2010;138: 790­4. Mikos M, Grzanka P, Sladek K, Pulka G, Bochenek G, Soja J, et al. High-resolution computed tomography evaluation of peripheral airways in asthma patients: comparison of focal and diffuse air trapping. Respiration 2009;77:381­8. Gomez M, Silvestri GA. Endobronchial ultrasound for the diagnosis and staging of lung cancer. Proc Am Thorac Soc 2009;6:180­6. Sammartino F. Macchiarini P. Primary tracheal tumors. Lung cancer, 4th ed. 2014:267­77. Szlubowski A, Kudal J, Kolodziej M, Soja J, Pankowski J, Obrochta A, et al. Endobronchial ultrasound-guided needle aspiration in the non-small cell lung cancer staging. Eur J Cardiothorac Surg 2009;35:332­5. Szlubowski A, Zieliski M, Soja J, Annema JT, Sonicki W, Jakubiak M, et al. A combined approach of endobronchial and endoscopic ultrasound-guided needle aspiration in the radiologically normal mediastinum in non-small-cell lung cancer staging ­ a prospective trial. Eur J Cardiothorac Surg 2010;37:1175­9. Aydogmus MT, Erkalp K, Sinikoglu SN, Usta TA, Ulger GO, Alagol A. Is ultrasonic investigation of transverse tracheal air shadow diameter reasonable for evaluation of difficult airway in pregnant women: a prospective comparative study. Pakistan J Med Sci 2014;30:91. Lie CH, Chao TY, Chung YH, Wang JL, Wang YH, Lin MC. New image characteristics in endobronchial ultrasonography for differentiating peripheral pulmonary lesions. Ultrasound Med Biol 2009;35:376­81. Agarwal A, Singh DK. Bronchoscopic topical steroid instillation in prevention of tracheal stenosis. J Anaesthesiol Clin Pharmacol 2014;30:91. Kang Y, Lee YK, Lee HS, Chae YK, Min J. Tracheal injury as a perforation of a newly formed tracheal diverticulum after tracheal ubation: a case report. Anesth Pain Med 2015;10:32­5. Andreassen AH, Ellingsen I, Nesje LB, Gravdal K, Ødegaard S. 3-D endobronchial ultrasonography ­ a post mortem study. Ultrasound Med Biol 2005;31:473­6. Purcell P, Meyer T, Allen C. Tracheal mass. JAMA Otolaryngol Head Neck Surg. 2015;141:291­2. Soja J, editors. Practical medicine, Krakow: the use of endobronchial ultrasound in the evaluation of remodeling in asthma, 2011.

Journal

Bio-Algorithms and Med-Systemsde Gruyter

Published: Dec 1, 2015

References