Evaluation of in vivo total and regional air content and distribution in primate lungs with high-resolution CT

The authors sought to determine whether gray-scale quantitative information from high-resolution computed tomography (CT) could reliably yield estimates of lung air content and help determine changes in air content with lung inflation and deflation. High-resolution CT images ( n = 40) of lungs of two anesthetized monkeys were obtained after inflation with known air volumes. Percentage air content was calculated for each voxel, and lung volumes and patterns of air distribution were determined. When corrected for pressure and temperature, high-resolution CT-based volumes correlated closely with inflation volumes ( r = 99; standard error = 3.4%). Patterns of regional change in air content demonstrated known patterns of ventilation. Although the high-spatial-frequency algorithm used in high-resolution CT enhances edges of structures and improves visualization of anatomic detail, gray-scale values from the same high-resolution CT data set remain a reliable index of regional lung attenuation.