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 Table of Contents  
ORIGINAL ARTICLE
Year : 2020  |  Volume : 4  |  Issue : 2  |  Page : 289-294

Multislice computed tomography multiplanar reconstruction chest and three-dimensional reconstruction imaging of the airway remodeling in evaluation of asthma and chronic obstructive lung disease


1 Department of Radiodiagnosis, Faculty of Medicine for Girls, Egypt
2 Department of Radiodiagnosis, Faculty of Medicine for Girls, Al-Azhar University, Cairo, Egypt
3 Department of Radiology, Fayoum Fever Hospital, Faculty of Medicine for Girls, Al-Azhar University, Cairo, Egypt

Date of Submission28-Apr-2020
Date of Decision14-May-2020
Date of Acceptance19-May-2020
Date of Web Publication29-Jun-2020

Correspondence Address:
Prof. Suzan A F Swelum
Department of Radiodiagnosis, Faculty of Medicine for Girls, Al-Azhar University, Cairo
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/sjamf.sjamf_48_20

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  Abstract 


Objective This study aims to estimate the role of multislice computed tomography multiplanar reconstruction and three dimensional in evaluation of the airway remodeling and lung parenchyma in patients with asthma and those with chronic obstructive lung disease.
Patients and methods Asthmatic patients (n=19) and patients with chronic obstructive pulmonary disease (COPD) (n=31) underwent chest high-resolution computed tomography. We selected the apical bronchus (B1) and the posterior basal bronchus (B10) of the right lung. A segmental bronchus was defined as the third-generation bronchus. Wall area (WA) was calculated as Ao−Ai. The percentage wall area (WA%) was calculated as (WA/Ao)×100 and then assessed for each generation from two bronchi.
Results Total WA% in patients ranged between 74.6 and 95.2, with a mean±SD of 84.9±5.5. Although the total WA% in patients with asthma was higher than in those with COPD (86.1±5.8 vs. 84.1±5.3), it was not statistically significant (P=0.231). Regarding the parenchymatous lung changes, these changes were detected in patients with both disease groups; Hounsfield unit ranged between −1042 and −855, with a mean±SD of −944.0±56.1. We demonstrated that COPD group had statistically significantly lower Hounsfield unit (mean±SD=−959.8±57.8) compared with bronchial asthma group (mean±SD=−919.1±34.1), with P=0.006.
Conclusion Quantitative computed tomography has been widely used as an imaging tool in patients with COPD and those with bronchial asthma. Now it is possible to analyze the lung parenchyma and airways quantitatively using digital data from computed tomography.

Keywords: bronchial asthma, chronic obstructive pulmonary disease, emphysema, quantitative computed tomography, wall area


How to cite this article:
Swelum SA, Ahmed AH, Abdullah ER. Multislice computed tomography multiplanar reconstruction chest and three-dimensional reconstruction imaging of the airway remodeling in evaluation of asthma and chronic obstructive lung disease. Sci J Al-Azhar Med Fac Girls 2020;4:289-94

How to cite this URL:
Swelum SA, Ahmed AH, Abdullah ER. Multislice computed tomography multiplanar reconstruction chest and three-dimensional reconstruction imaging of the airway remodeling in evaluation of asthma and chronic obstructive lung disease. Sci J Al-Azhar Med Fac Girls [serial online] 2020 [cited 2020 Jul 12];4:289-94. Available from: http://www.sjamf.eg.net/text.asp?2020/4/2/289/288284




  Introduction Top


Bronchial asthma and chronic obstructive pulmonary disease (COPD) is a prevalent disease condition that is caused owing to respiratory air-flow limitation and is characterized by airway inflammation. This disease develops with dyspnea and oxygenation impairment, thus inflicting great burden to patients [1]. COPD is a complex condition with a wide spectrum of clinical presentations and pathological features unified under the spirometric definition of air-flow obstruction. Airway narrowing and parenchymal destruction are recognized as the mechanisms responsible for air-flow obstruction in COPD, but they cannot be distinguished by standard spirometry. In recent years, chest computed tomography (CT) allows to depict and measure in vivo the lung pathologic changes of COPD by quantifying parenchymal destruction, the direct sign of emphysema, as well as bronchial wall thickening and gas trapping, which represent direct and indirect signs of conductive airway disease, respectively [2]. Asthma is a chronic inflammatory disease of the airway that is characterized by airway inflammation, airway hyperresponsiveness, and reversible air-flow limitation. Chronic inflammation in asthma can lead to changes in airway structure. Airway remodeling, which includes narrowing of the airways and bronchial wall thickening, is a consequence of chronic injury, and repair may be reversible or irreversible. These changes affect all parts of the tracheobronchial tree but are initially located in the small airway and progress to the large airway. Distal small airways (<2 mm in diameter) become narrow or obstructed during expiration, leaving redundant air in the lungs, which is known as air trapping [3]. With recent advances in imaging technology, quantitative CT analysis can be used to provide detailed information about airway changes in a noninvasive manner. Not only can the location of air trapping be observed but also the changes in airway structure can be intuitively assessed [3].


  Aim Top


The aim was to estimate the role of multislice CT multiplanar reconstruction (MPR) and three dimensional in evaluation the airway remodeling and lung parenchyma in patients with asthma and those with chronic obstructive lung disease.


  Patients and methods Top


It was a prospective study carried out at the radiology department of Al-Zahraa University Hospital. After obtaining local medical ethics committee approval and written informed consent from all patients in the study, 50 patients diagnosed as having COPD or bronchial asthma were eligible in the study, whereas patients who refused to be involved in the study, had other chest diseases, or complicated patients such as those with orthopnea were excluded from the study.

Imaging and imaging analysis

  1. Postprocessing measurements of bronchial wall thickness:
    1. Reconstruction data were transferred to the Vitrea workstation and reconstructed into three-dimensional bronchial tree. On the workstation monitor, we could identify the bronchial tree in the axial, sagittal, and coronal MPR reformats images with a window width of 1500 Hounsfield unit (HU) and a window level of −700 HU. A narrower window width (750–1000 HU) may be useful for detecting or excluding early emphysema.
    2. The selected bronchial pathway was automatically converted to a curved MPR image. The bronchial long-axis image appeared as a straight pathway. We obtained short-axis images that were exactly perpendicular to the long axis at any site.
    3. After the process, we obtained values for inner diameter (L) and outer diameter (D) of the selected bronchi, and then inner luminal area (Ai) and outer luminal area (Ao) of airway were calculated.
    4. Mean values of Ai and Ao in each generation were calculated at a point, the observer randomly chose, that had completely depicted the outline of the bronchial wall. We could measure the third, fourth, and fifth generation in selected bronchi on per participant. Wall area (WA) was calculated as Ao−Ai. The percentage wall area (WA%) was calculated as (WA/Ao)×100. We then assessed the value of WA% for each generation from two bronchi.
    5. To measure airway dimensions, we selected two bronchi: the apical bronchus (B1) and the posterior basal bronchus (B10) of the right lung. In this study, a segmental bronchus was defined as the third-generation bronchus at both B1 and B10. Analysis was limited to the third through fifth generations, and the number of detected bronchi was low after fifth generation.
    6. All airway dimensions were measured by one observer in a blinded fashion. When the measurements were repeated, the observer was blind to the previously obtained measurement data.
  2. Assessment of parenchymatous lung changes:
    1. In our study, we assessed parenchymatous lung changes quantitatively to diagnose areas of air trapping and emphysematous lung changes at the level of the entire lung.


Data collection and analysis

Data were collected and statistically analyzed.


  Results Top


A total of 50 patients were included in this study with the age of participating patients ranged between 20 and 61 years old, with a mean±SD age of 45.9±13.2 years. Regarding sex, most of the participants were males [31 (62.0%)] and 19 (38.0%) were females.

Total WA% in patients ranged between 74.6 and 95.2, with a mean±SD of 84.9±5.5. Although the total WA% in patients with asthma was higher than in those with COPD (86.1±5.8 vs. 84.1±5.3), it was not statistically significant (P=0.231). These results are represented in [Table 1] and [Figure 1],[Figure 2],[Figure 3].
Table 1 Comparison between study groups regarding wall area parameters

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Figure 1 HRCT airway cross-section measurements of D, external diameter; L, internal (luminal) diameter; WT, wall thickness; AO, total airway area; AL, luminal area; and WA, wall area [4]. HRCT, high-resolution computed tomography.

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Figure 2 MSCT MPR (a–d) measurements of cross-section of right B1 generation 3, 4, 5). MPR, multiplanar reconstruction; MSCT, multislice computed tomography.

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Figure 3 WA parameters in the study cases. WA, wall area.

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Regarding the parenchymatous lung changes, these changes were detected in patients with both disease groups. HU ranged between −1042 and −855, with a mean±SD of −944.0±56.1. We demonstrated that COPD group had statistically significantly lower HU (mean±SD=−959.8±57.8) compared with bronchial asthma group (mean±SD=−919.1±34.1), with P=0.006 ([Table 2] and [Figure 4]).
Table 2 Difference in Hounsfield unit parameter between study groups

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Figure 4 Difference in HU parameters between study groups. HU, Hounsfield unit.

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For differentiating bronchial asthma from COPD, total WA% had a fair discriminative power (area under the curve=0.604). The optimal WA% cutoff point for differentiating bronchial asthma from COPD was 84, which yielded sensitivity of 63.2% and specificity of 64.5%.

On the contrary, HU had a good discriminative power for differentiating bronchial asthma from COPD (area under the curve=0.692). The optimal cutoff point was −964.5, with 84.2 and 63.5% as sensitivity and specificity, respectively. These findings are represented in [Table 3] and [Figure 5].
Table 3 Sensitivity and specificity of wall area and Hounsfield unit in differentiating between patients with bronchial asthma and chronic obstructive pulmonary disease

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Figure 5 ROC curve for differentiating bronchial asthma from COPD. COPD, chronic obstructive pulmonary disease; ROC, receiver operating characteristic.

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  Discussion Top


Asthma and COPD are chronic diseases characterized by airway inflammation and air-flow obstruction, which are common in the general population [5]. In our study, we describe the airway morphometry and lung densitometry of asthmatic patients and patients with COPD. Based on the results of the study by Telenga et al. [6], a normal bronchial wall thickness in healthy participants ranges between 0.18 and 0.23 mm, and the normal range for WA% is between 44 and 70%.The results of our study suggest that WA% is greater in asthmatics and patients with COPD than normal range. The mean value of this parameter was significantly higher in patients with asthma and those with COPD when the results of all individual airway measurements were analyzed, with the total WA% in asthma higher than in those with COPD with fair discriminative power. Supporting our results, Hartley et al. [7] researched 171 asthmatic patients, 81 with COPD, and 49 healthy participants (recruited from a single center) who underwent volumetric whole lung scans by using multidetector CT. Images were reconstructed and postprocessing was performed. It was found that proximal airway WA% was significantly increased in asthmatic patients and patients with COPD compared with that in healthy controls. CT airway walls have been demonstrated to be thicker and are significantly correlated with asthma duration and severity and in COPD. CT airway wall thickening has been shown to be significantly associated with lung function and the frequency of exacerbations, as showed in the study by Herth et al. [8]. In the study by Gorska et al. [9], results revealed that airway remodeling in asthma and COPD is triggered by uncontrolled inflammation and results in airway narrowing, and high-resolution CT has been found useful in the quantitative and qualitative assessment of airway and lung tissue remodeling in asthma and COPD. Moreover, it was also found that besides BWT measurement, this method gives the possibility of calculating other parameters, like the bronchial lumen. Our results are in agreement with Ostridge [10], who found that there were significantly increased wall thickness and WA in participants with COPD and in agreement also with another study done by Da Silva et al. [11], who found bronchial thickening in 69.2% of the 65 patients with CODD. Jobst et al. [12] and Díaz [13] in their studies when assessing the relationship between airway inflammation and remodeling in patients with asthma and COPD found that WA and wall thickness were slightly higher in the asthma group, but the differences were not significant. Regarding the parenchymatous lung changes, these changes were detected in patients with both disease groups; the HU ranged between −1042 and −855, with a mean of −944.0±56.1. It is demonstrated that the COPD group had statistically significantly lower HU, with a mean of −959.8±57.8 compared with the bronchial asthma group, with a mean of −919.1±34.1. The reported results of our study agreed with Hartley et al. [7], who mentioned that air trapping measured based on mean lung density expiratory/inspiratory ratio was significantly increased in patients with COPD [mean, 0.922 (SD, 0.037)] and asthmatic patients [mean, 0.852 (SD, 0.061)] compared with that in healthy participants [mean, 0.816 (SD, 0.066), P<0.001]. Emphysema assessed based on lung density measured by using HU was a feature of COPD only. Additionally, our study is concordant with a study done by Xie et al. [14], which found that patients with COPD had a higher extent of emphysema on quantitative CT than patients with asthma or controls. Emphysema was quantified by percentage of lung voxels with CT attenuation value below −950 HU (%LAA-950). It was also in agreement with Choi et al. [15], who in a study performing inspiratory and expiratory quantitative CT analysis of 75 asthmatic patients, 215 patients with COPD, and 94 healthy participants found that quantitative CT imaging-based variables were found to be effective in differentiating asthmatics from healthy participants as well as COPD patients from asthma patients. Functional metrics, especially density-based metrics, obtained at lobar/global regions, were found to be significantly different between the two disease populations. Compared with asthma, COPD has significantly more lung emphysema, more small-airway disease, with reduced tissue fraction and regional lung deformation.


  Conclusion Top


Multidetector CT chest with three-dimensional reconstruction and MPR permits early and accurate detection of airway remodeling and parenchymatous lung changes accompanied with COPD and bronchial asthma, aiming to contribute in choosing the right treatment for better improvement.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]



 

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