Quantitation of Emphysema with Three-dimensional CT Densitometry: Comparison with Two-dimensional Analysis, Visual Emphysema Scores, and Pulmonary Function Test Results

Abstract

PURPOSE: To compare lung densitometric measurements that use a three-dimensional (3D) reconstruction of the lungs with those obtained from analysis of two-dimensional (2D) computed tomographic (CT) images, visual emphysema scores, and data from pulmonary function tests.

MATERIALS AND METHODS: Thoracic helical CT scans were obtained in 60 adult patients (35 with no visual evidence of emphysema and 25 with emphysema). The lungs were reconstructed as a 3D model on a commercial workstation, with a threshold of −600 HU. By analysis of histograms, the proportions of lung volumes with attenuation values below −950, −910, and −900 HU were measured, in addition to mean lung attenuation. These values were compared with lung densitometric results obtained from 2D CT images, visual emphysema scores, and data from pulmonary function tests.

RESULTS: Quantitation of emphysema with 3D reconstruction was efficient and accurate. Correlation was good among densitometric quantitation with 3D analysis, that obtained with 2D analysis (r = 0.98–0.99), and visual scoring (r = 0.74–0.82). Correlation was reasonable between 3D densitometric quantitation and the diffusing capacity of the lungs for carbon monoxide (Dlco) (r = −0.57 to −0.64), total lung capacity (r = 0.62–0.71), forced expiratory volume in 1 second (FEV1) (r = −0.57 to −0.60), and the ratio of FEV1 to forced vital capacity (FVC) (r = −0.75 to −0.82). The visual CT quantitation of emphysema correlated best with Dlco (r = −0.82) and FEV1/FVC (r = −0.89).

CONCLUSION: Lung densitometry with 3D reconstruction of helical CT data is a fast and accurate method for quantifying emphysema.