COMPARISON OF DIFFERENT COMPUTED-TOMOGRAPHY SCANNING METHODS FOR QUANTIFYING EMPHYSEMA

Computed tomography (CT) is used to detect emphysematous changes in th e lungs of living patients. It is therefore important to develop a sta ndard method for the radiographic quantification of emphysematous lesi ons using CT. The authors determine the best CT scanning methods for a ssessing the degree of pulmonary emphysema. Computed tomography scanni ng was performed in 85 consecutive patients with stable chronic obstru ctive pulmonary disease. Scans were obtained using 2-mm or 5-mm collim ation, at full inspiration or full expiration, and with standard or hi gh spatial-resolution reconstruction images (eight images each). Emphy sema was then assessed by visual scoring using a five-point scale for each lung. Emphysema was scored as significantly less severe using sta ndard reconstruction images. There were no significant differences in CT-scored emphysema on scans obtained with 2-mm and 5-mm collimation. Emphysema was scored as significantly less severe on expiratory scans. The postbronchodilator forced expiratory volume in one second value c orrelated better with emphysema scored on expiratory scans. Computed t omography-scored emphysema obtained by all methods correlated well wit h the diffusion capacity and total lung capacity, regardless of the me thod used. Using a visual scoring system with a five-point scale, narr ow collimation is probably not necessary for the quantification of emp hysema, although a high spatial-resolution reconstruction appears to b e of value. Scans obtained in exhalation appear to underemphasize the severity of emphysema.