High Resolution Computed Tomography and Chronic Obstructive Pulmonary Disease
Introduction Chronic obstructive pulmonary disease (COPD) is a preventable and treatable respiratory disease with some significant extrapulmonary effects that may contribute to the severity in individual patients. Its pulmonary components are characterized by airflow limitation that is not fully reversible. COPD is a leading cause of morbidity and mortality worldwide. The economic and social burdens due to it are substantial and anticipated to increase in the coming decades due to continued
... ue to continued exposure to COPD risk factors and the changing age profile of the world's population. COPD mortality trends generally track several decades behind smoking trends. In US in 2000, more women than men died of COPD or its related complications. COPD comprise of a heterogeneous group of disorders conventionally including emphysema, chronic bronchitis, peripheral airways disease and pulmonary vascular disease. It is a disease state that has seen significant changes in defining and excluding criteria over past 50 years. Spirometry, the most frequently used tool to diagnose COPD and to assess response to treatment in these patients, can provide only functional assessment. In contrast to spirometry, radiological imaging allows for regional assessment of the various compartments involved i.e. airways, parenchyma and vasculature. High-resolution computed tomography (HRCT) is recommended for the non-invasive and sensitive assessment of morphological changes in emphysema and has been shown to correlate well with pathology. With the advent of new imaging techniques like multi-detector row CT (MDCT), contrast-enhanced CT methods, spirometric controlled MDCT, use of Xenon gas to assess regional ventilation of the lungs, magnetic resonance imaging (MRI) of the lung developing its own arsenal like hyperpolarized He-3 MRI -new avenues are being opened up which are now increasingly supplemented with advanced and dedicated softwares. Advantages of high resolution computed tomography At present the diagnostic criteria recommended by the Global Strategy for the Diagnosis, Management and Prevention of Chronic Obstructive Lung Disease (GOLD guidelines) do not consider CT findings during initial diagnostic assessment (Pauwels & Buist 2001) and principally rely on spirometry. However, enough scientific literature suggests that HRCT is an important and indispensable tool for evaluation of COPD. Some of the uses of HRCT are described below in next sections. www.intechopen.com Bronchitis 150 Identifying causes of airway obstruction other than COPD Chronic airflow obstruction may be caused by a wide variety of diseases like bronchiectasis, upper airway lesions, bronchiolar diseases, interstitial lung diseases etc that may often produce clinical symptoms inseparable those due to COPD. HRCT can clearly identify different causes of airflow obstruction. Kurashima et al (2005) showed in 516 consecutive patients whose postbronchodilator FEV1/FVC was less than 70%, HRCT was able to identify 12.7% of patients with pulmonary diseases other than COPD including sarcoidosis, diffuse panbronchiolitis and pneumoconiosis. The exact diagnosis of underlying pathology leading to air flow obstruction is essential in management and to predict response to treatment in these patients. Identification of emphysema before appearance of clinical symptoms HRCT can detect pulmonary emphysema even in asymptomatic smokers with normal lung functions. Recent GOLD guidelines have abolished stage 0 that included asymptomatic patients who were smokers and had normal lung functions; however, Sverzellati et al (2007) observed that 13/18 subjects with stage 0 had emphysema detected over HRCT scan. It reflects that HRCT is a sensitive tool to detect emphysema before it is manifesting clinically or with deranged pulmonary functions. Detection of early emphysema may be of enormous value to prevent its progression by smoking cessation and medical intervention (Morgan 1992).