Assessment of the severity of pulmonary emphysema by computed tomography

Pulmonary emphysema is defined as an abnormal enlargement of alveolar spaces distal to the terminal bronchioles, with alveolar wall disruption and without obvious fibrosis. Clinico-functional evaluation and chest radiographic diagnosis are not highly accurate in detecting emphysema and in establishing the extent of the process of alveolar destruction. Several computed tomography (CT) techniques are now available for detection and quantitative assessment of emphysema. The results appear to correlate significantly better than chest radiography with functional impairment and pathological score. Many options have been proposed by different authors regarding CT technique. The choice, however, is essentially between inspiratory high resolution CT (HRCT) with a visual scoring system, and automated quantitative evaluation by means of a "density mask" (DM) program. This paper presents the state of the art on CT quantification of pulmonary emphysema and briefly discusses the technical options and parameters to be used, together with the problems to be solved.