الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
COPD is a heterogeneous, common, preventable and treatable disease that is characterized by persistent respiratory symptoms and airflow limitation that are due to airway and/or alveolar abnormalities, usually caused by significant exposure to noxious particles or gases
Assessment of pulmonary function is essential for the diagnosis and characterization of COPD. In general, spirometry is the method most commonly used to detect airway obstruction; it is a relatively simple, repeatable, noninvasive, and inexpensive technique that allows a global assessment of functional changes. The primary parameters of diagnostic assessment at spirometry are forced expiratory volume in the 1st second (FEV1) and forced vital capacity (FVC). Reductions in FEV1, FVC, and the ratio of FEV1 to FVC (hereafter, FEV1/FVC ratio) are hallmarks of airway obstruction. The criterion for a diagnosis of COPD is an FEV1/FVC ratio of less than 70%. In addition to these parameters, measurement of the diffusing capacity of the lung for carbon monoxide allows the detection of emphysema in patients with airflow obstruction. However, spirometry does not provide regional information about the distribution of emphysema
In contrast, CT allows a regional assessment of each lung compartment, including the airways, parenchyma, and vasculature. In addition, CT is more sensitive than spirometry for detecting extent of emphysema. Yet, it is subjective tool. Therefore, emphysema quantification on CT scans may be an important complimentary tool for the diagnosis and staging of COPD as an objective tool.
The choice between a volumetric lung CT (VLCT) and PFTs in the diagnosis and monitoring of respiratory conditions is an important one. While PFTs provide essential diagnostic information, such as airway obstruction, gas exchange, and respiratory mechanics, they do not provide in-depth visualization of the lungs. VLCTs, on the other hand, provide high-resolution images of lung structure and tissue.
A VLCT can detect structural and functional information of the lung parenchyma not provided by PFTs. For example, VLCTs can identify infiltrates, interstitial thickening, bronchial wall thickening, and volume changes, while PFTs cannot. In addition, VLCTs are highly sensitive in identifying early signs of lung diseases, such as emphysema, that are not detected by PFTs.
VLCTs and PFTs may also be used together to provide a more comprehensive assessment of respiratory conditions. For example, PFTs may be used to assess airway obstruction and ventilation, while VLCTs can provide additional regional information on regional lung function. Furthermore, VLCTs also provide quantitative measures of regional volume and ventilation to complement traditional PFTs.