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Objective: To evaluate, in patients with chronic obstructive lung disease or chronic bronchitis, inspiratory helical CT with 3D postprocessing, to measure lung volumes and the amount of emphysema and to compare these measurements with lung function tests., Material and Methods: Seventeen patients with chronic obstructive lung disease disease or chronic bronchitis underwent pulmonary function tests and helical CT after a full inspiration with 3D postprocessing (lower threshold -1024 HU, upper thresholds -200, -300 and -400 HU). Lung inspiratory volumes (TLC-CT) were determined for each model; the amount of emphysema was evaluated by means of an automatic score and a visual score with HRCT., Results: There is a good correlation between automatic and visual scores (p < 0.001); the automatic score had a good correlation with lung function tests, above all with total lung capacity (r = -0.56; p = 0.01) but the visual score had a much closer correlation with DLCO (r = -0.70; p < 0.001). TLC-CT had a significant correlation with pletismographic TLC (TLC-P); the upper threshold -200 HU was more correct (TLC-P = 8011 cc.; TLC-CT 200 = 7138 cc.; r = 0.83; p < 0.001). The volume change of 3D model was about 230 cc. per 100 HU (p < 0.001) modifying upper thresholds, but no change was observed in the volume occupied by emphysema and the percentage of emphysema presented minimal, clinically non significant modifications., Discussion and Conclusions: In emphysematous patients, the helical CT with 3D model construction is a good technique to evaluate lung volumes and to quantify emphysema with automatic score; this one, however, probably underscores the extent of pathology; therefore, the addition of a visual score with HRCT is probably worthwhile.

Computed Tomography (CT) has been proved to be the most accurate imaging modality to diagnose emphysema in vivo. Our study was aimed at comparing different CT methods for pulmonary emphysema quantification in patients with severe chronic obstructive pulmonary disease (COPD). Forty-six consecutive inpatients affected with COPD underwent high resolution CT (HRCT). Three scans were acquired at 3 preselected anatomic levels at both full inspiration and expiration. Three different observers were asked to subjectively evaluate, under blind conditions, the extent alone and both the severity and the extent of emphysema on the 6 scans. HRCT findings were also analyzed quantitatively by measuring the mean CT number in Hounsfield Units (HU) and the % of lung area with CT numbers < -900 HU (pixel index). Quantitative CT data were compared with reference values obtained in 7 normal nonsmokers. The CT visual score of emphysema exhibited medium-high interobserver reproducibility with correlation coefficients ranging from 0.80 to 0.96 and a good correlation with pulmonary function tests, particularly relative to the assessment of the extent of emphysema alone as expressed by one observer. CT quantification demonstrated an excellent correlation with functional indices of expiratory airflow, lung volumes and diffusion coefficients (p < 0.001). The expiratory measurements were better than the inspiratory ones while the analysis of both CT number and pixel index gave comparable results. Only the CT expiratory quantitative data allowed to differentiate the patients affected with COPD from the controls. In conclusion, the severity of emphysema as expressed by CT correctly reflects the functional impairment of patients with severe COPD.(ABSTRACT TRUNCATED AT 250 WORDS)

Computed Tomography scanners can be calibrated to provide reproducible measurements for the quantitative analysis of lung density. We measured in square centimeters the pulmonary density areas for each interval of values expressed in Hounsfield Units and obtained some histograms representing the "respiratory curves" for full inspiration and full expiration. The study population had been divided into three groups according to their clinical conditions. Group A: 12 normal subjects, aged 20-40, non-smokers; Group B: 23 patients, aged 40-65, smokers, asymptomatic or slightly asthmatic; Group C: 19 patients, aged 55-75 hospitalized with chronic obstructive pulmonary disease. The respiratory curves obtained at full expiration appeared to be completely different in the three groups resulting more significant than those obtained at full inspiration. We conclude that the histograms obtained by measuring the pulmonary density areas in full expiration at preselected intervals of HU values can be useful as a screening test as well as to quantify pulmonary emphysema.