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Imaging Studies in Emphysema

¹ Department of Radiology, University of California San Diego, San Diego, California

Correspondence and requests for reprints should be addressed to Paul J. Friedman, M.D., Department of Radiology, UCSD Medical Center, 410 Dickinson Street, San Diego, CA 92103-8749. E-mail pfriedman{at}ucsd.edu

ABSTRACT

Definitions of types of emphysema within the framework of chronic obstructive pulmonary disease are given. The classic findings on the chest radiograph are described, and the advances in sensitivity and specificity achieved with computed tomography (CT) scanning are noted. The "density mask" and the "percentile point" measurements rely on the densitometric property of X-rays, but the scan also shows the severity and distribution of low-attenuation regions that usually represent pathologic emphysema. The alteration of absolute density with changes in lung inflation, CT slice thickness, collimation, and reconstruction algorithm make comparison between CT scans and across studies more difficult. Nevertheless, quantitative CT has superseded subjective scoring of scan appearance by readers as a sensitive way to measure emphysema.

Key Words: radiology • emphysema • COPD • quantitative CT