Original Article

Quantitative assessment of pulmonary perfusion using dynamic contrast-enhanced CT in patients with chronic obstructive pulmonary disease: correlations with pulmonary function test and CT volumetric parameters

Acta Radiologica 2015, Vol. 56(5) 573–580 ! The Foundation Acta Radiologica 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0284185114535208 acr.sagepub.com

Yu Guan1,*, Yi Xia1,*, Li Fan1, Shi-yuan Liu1, Hong Yu1, Bin Li1,*, Li-ming Zhao2 and Bing Li2

Abstract Background: Pulmonary function test (PFT) is commonly used to help diagnose chronic obstructive pulmonary disease (COPD) and other lung diseases. However, it cannot be used to evaluate regional function and morphological abnormalities. Purpose: To quantitatively evaluate pulmonary perfusion imaging using dynamic contrast-enhanced (DCE) computed tomography (CT) and observe its correlations with PFT and CT volumetric parameters in COPD patients. Material and Methods: PFT and CT pulmonary perfusion examination were performed in 63 COPD patients. Perfusion defects were quantitated by calculating the CT value ratio (RHU) between perfusion defects (HUdefect) and normal lung (HUnormal). Volumetric CT data were used to calculate emphysema index (EI), total lung volume (TLV), and total emphysema volume (TEV). Emphysematous parenchyma was defined as the threshold of lung area lower than –950 HU. Correlations between RHU and TLV, TEV, EI, and PFT were assessed using Spearman correlation analysis. Results: The positive rate of perfusion defects on CT perfusion images was higher than that of emphysema on CT mask images (2 ¼ 17.027, P < 0.001). The Spearman correlation test showed that RHU was positively correlated with FEV1 (R ¼ 0.59, P < 0.001), FEV1% Predicted (R ¼ 0.61, P < 0.001), FVC (R ¼ 0.47, P ¼ 0.002), and FEV1/FVC (R ¼ 0.65, P < 0.001), and negatively correlated with EI (R ¼ –0.67, P < 0.001). Conclusion: CT perfusion imaging is more sensitive in detecting emphysema that is inconspicuous on CT images. RHU is correlated with PFT and CT volumetric parameters, suggesting that it is more sensitive in detecting early COPD changes and may prove to be a potential predictor of focal lung function.

Keywords Chronic obstructive pulmonary disease, emphysema, pulmonary function test, computed tomography Date received: 16 October 2013; accepted: 18 April 2014

Introduction Chronic obstructive pulmonary disease (COPD) is a common and progressive condition that is currently the fourth leading cause of death worldwide (1). Pulmonary function test (PFT) is the most important clinical test for COPD at present, but it is unable to determine pathological changes, regional function, and morphological abnormalities (2). Imaging examination has a great advantage over PFT in assessing regional, morphologic, and functional changes in

1 Department of Radiology, Changzheng Hospital of the Second Military Medical University, Shanghai, PR China 2 Department of Respiration Medicine, Changzheng Hospital of the Second Military Medical University, Shanghai, PR China *

These authors are equal contributors.

Corresponding author: Li Fan, Department of Radiology, Changzheng Hospital of the Second Military Medical University, No. 415 Fengyang Road, Shanghai 200003, PR China. Email: [email protected]

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COPD. Altered pulmonary blood flow is one of the most important pathological changes in COPD (3), and therefore assessment of the pulmonary perfusion status is very useful to gain a comprehensive understanding about the development and progression of COPD (4,5). The perfusion status in COPD patients remains elusive. Various approaches for determining pulmonary perfusion have been described, such as radionuclide scintigraphy, dynamic computed tomography (CT) scan, and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). Radionuclide scintigraphy used to be the golden standard for assessment of pulmonary perfusion, but it has substantial limitations with respect to low spatial and temporal resolution. MRI for assessment of lung perfusion avoids exposure to ionizing radiation. However, the low proton density of lung parenchyma usually leads to poor signal, making it impossible to display the small anatomical structures of the lung clearly. CT is able to show minute anatomical structures due to high spatial resolution and provide quantitative and functional information (6). Quantitative CT of emphysematous destruction can provide emphysema index (EI), total lung volume (TLV), total emphysema volume (TEV), mean lung density (MLD), and other parameters. The relationship between the extent of emphysema on quantitative CT and the presence of pathologic emphysema is well established. Bankier et al. (7) demonstrated that quantitative CT measurements had better correlations with macroscopic measurements of emphysema as compared with visual CT scoring. Many studies (8,9) have explored correlations between the extent of emphysema and different pulmonary function parameters. The dynamic contrastenhanced (DCE)-CT technique has been proposed for the assessment of lung perfusion on the basis of contrast enhancement of pulmonary parenchyma during the initial passage of a bolus of contrast material through the pulmonary circulation. Several studies (10,11) have reported the impairment of CT perfusion in COPD patients with dual-source CT, but few studies have reported CT perfusion imaging of the pulmonary parenchyma by quick dynamic scanning and subtraction techniques. The purpose of this prospective study was to quantitatively evaluate CT imaging of pulmonary parenchyma perfusion and explore its correlations with PFT and CT volume parameters in COPD patients.

Material and Methods Patients A series of 63 consecutive patients who were admitted in the same Department of Respiration Medicine in one hospital (53 men, 10 women; age range 45–79 years;

mean age 65  9 years) were recruited in this prospective study from May 2011 to January 2012. The diagnosis of COPD was according to the result of spirometry as FEV in 1 s (FEV1)/forced vital capacity (FVC) (%)

Quantitative assessment of pulmonary perfusion using dynamic contrast-enhanced CT in patients with chronic obstructive pulmonary disease: correlations with pulmonary function test and CT volumetric parameters.

Pulmonary function test (PFT) is commonly used to help diagnose chronic obstructive pulmonary disease (COPD) and other lung diseases. However, it cann...
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