ASSESSMENT OF THE PROGRESSION OF EMPHYSEMA BY QUANTITATIVE-ANALYSIS OF SPIROMETRICALLY GATED COMPUTED-TOMOGRAPHY IMAGES

RATIONALE AND OBJECTIVES. The authors assessed the progression of pulm onary emphysema by means of quantitative analysis of computed tomograp hy images. METHODS. Twenty-three patients suffering from emphysema due to an alpha(1)-antitrypsin deficiency, aged 45 +/- 7 years and exsmok ers, were scanned twice with a 1-year time interval, At 90 % of the vi tal lung capacity, slices with a thickness of 1.5 mm were acquired at the level of the carina and 5 cm above the carina; slices with a thick ness of 1 cm mere acquired 5 cm below the carina, The entire lung was scanned spirally at a respiratory status, corresponding with 75% of th e total lung capacity at baseline, The mean lung densities (MLD) were calculated in an objective manner with new analytic software featuring automated detection of the lung contours. RESULTS. Mean lung densitie s decreased by 14.2 +/- 12.0 Hounsfield units (HU; P < 0.001) above th e carina, by 18.1 +/- 14.4 HU (P < 0.001) at the carina level, by 23.6 +/- 15.0 HU (P < 0.001) below the carina, and by 12.8 +/- 22.2 HU (P < 0.01) for the entire lung, The decrease in MLD was most obvious in t he lower lung lobes, For the same patient group, the annual decrease i n the forced expiratory volume (FEV(1)) and the carbon monoxide-diffus ion were 120 +/- 190 mt (P < 0.01) and 10 +/- 70 mmol/kg/minute (P < 0 .2), respectively. No significant correlation was found between the de crease in MLD and the decrease in FEV(1). CONCLUSIONS. Progression of emphysema can be assessed in an objective manner based on the mean lun g density (MLD), measured from computed tomography volume scans as wel l as from single-slice scans, Mean lung density has proved to be more sensitive than FEV(1) and carbon monoxide-diffusion.