Quantitation of Emphysema by Computed Tomography Using a “Density Mask” Program
Emphysema is defined as “a condition of the lung characterized by abnormal permanent enlargement of the airspaces distal to the terminal bronchioles, accompanied by destruction of their walls, and without obvious fibrosis. Computed tomography has been shown to be a sensitive technique in evaluating the presence and severity of emphysema. On CT, emphysema is characterized by the presence of areas of abnormally low attenuation. Recently, M tiller et al used a GE 9800 CT scanner computer program “density mask” to outline and quantitate areas of emphysema on CT. Using this technique, they found that areas with attenuation of less than — 910 HU on CT scan correlated closely with the pathologic assessment of emphysema on the corresponding slice of the resected lung specimens (r = 0.90). The method also allows objective quantitation of the overall lung volume on CT, as well as the percentage of lung with emphysema.
In this study, we used the CT “density mask” program in 85 patients to quantitate the overall extent of emphysema in both lungs and correlated the CT quantitation of emphysema with pulmonary function tests. Twenty-five of these 85 patients were included in the original description of the “density mask” method to assess emphysema.
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