Can computed tomography quantify pulmonary emphysema?

In the last decade, several studies have suggested the possible role of computed tomography (CT) in the detection and the quantification of pulmonary emphysema. In order to verify whether this new method is adequately validated, this article gives an overview of these studies. The review shows that most of the studies used conventional CT and were based on visual scoring. Only a few were based on high resolution CT (HRCT) or concerned objective measurements of computed density. In addition, only a few studies included normal subjects and distinguished centrilobular from panlobular emphysema. The number of scans obtained in each study is extremely variable, whilst the minimum number necessary to provide accurate results remains unknown. Recently, automatic objective procedures which are truly quantitative and are applicable to HRCT have been made available. They should take the place of subjective scoring methods but further studies, based on macroscopic as well as on microscopic comparisons, are needed to validate and to standardize these techniques.