CT Measurements of Lung Density in Life Can Quantitate Distal Airspace Enlargement—An Essential Defining Feature of Human Emphysema

We used a computerized microscopic image analysis system to directly measure the surface area of distal air spaces in methacrylate-embedded blocks randomly selected from inflation-fixed lobes that were resected from 45 patients as treatment of their peripheral lung tumors. In 28 of these patients, a preoperative computer tomography (CT) scan, at 6 and 10 cm below the sternal notch, was used to generate frequency histograms of CT numbers (measured as EMI units), a measure of lung density, in pixels from the lung or lobe that was subsequently resected. A similar CT number histogram was also derived from the lateral two fifths of the area of lobe/lung that was to be resected. The EMI unit that defined the lowest fifth percentile of this latter histogram correlated (n = 28, r = −0.77, p < 0.001) with the mean value of the surface area of the walls of distal airspaces per unit lung volume (AWUV) in the five 1 mm × 1 mm microscopic fields with the lowest AWUV values, out of the 20 to 35 such fields examined in ...