Method for analysis and display of distribution of emphysema in CT scans

A novel method for the assessment and display of the distribution of emphysema in low-dose helical CT scans has been developed. The automated system segments the lung volume and estimates the degree of emphysema as a function of slice position within the lung. Eighty low-dose (120 kVp, 40 mA) high-resolution (2.5 mm slice thickness) CT scans were randomly selected from our lung cancer screening program. Three emphysema assessments were performed on each scan: the traditional method of averaging the degree of emphysema on four pre-selected CT slices, the total volumetric percentage of emphysema, and a graphical display of emphysema burden as a function of slice position based on a sliding window algorithm. The traditional four-slice estimates showed a high correlation (0.98) with the total volumetric percentages, yet provided limited spatial information. In those cases with a higher overall percentage of emphysema, the distribution within the lung as quantified by the new method was more skewed than that of less severe cases or normals. Analysis and display of the spatial distribution of emphysema allows for assessment of emphysema burden within each lung zone, which may be useful for quantitating the type of emphysema and the progression of disease over time.