ABSTRACT
Chronic obstructive pulmonary disease (COPD) is a slowly progressive disorder
characterized by airway obstruction resulting from some combination of pulmonary
emphysema and small airways disease. Although it may induce some changes on
radiographs, chronic bronchitis has a purely clinical definition and is not a
radiological diagnosis. By contrast, emphysema is defined anatomically and is best
detected by chest radiography and computed tomography (CT). The CT is not only
the primary and most widely used imaging technique to assess the presence and
extent of emphysema: it may also be useful in differentiating COPD patients who
have emphysema-predominant disease from those having airway remodeling-
predominant disease (1-4). As surgical and endoscopic treatment of emphysema
progresses, it becomes necessary to characterize emphysema in an objective and
reproducible manner. Besides, since pharmacological disease-modifying treatments
may be soon available, it could be helpful to detect emphysema before symptoms or
physiologic consequences have developed, and to quantify it to assess the progression
of disease and the influence of treatments. A number of recent and evolving
pulmonary imaging methods have the potential to provide quantitative methods for
assessing extent and distribution of emphysema and dimensions of airways on CT.
However, despite numerous and extensive studies, these methods have not yet been
standardized (5). Single photon emission CT (SPECT) and magnetic resonance (MR)
may provide functional displays of regional ventilation perfusion abnormalities (6).
Diffusion-weighted MR images using hyperpolarized gas seem to be very promising
to detect early emphysema in smokers before clinical, functional, and radiological
abnormalities (7).
