Purpose: To quantitatively assess the morphologic changes in the lungs after lung volume reduction surgery and determine whether changes at quantitative computed tomography (CT) reflect changes in lung function.
Materials and methods: In 10 patients, chest CT images were obtained at full inspiration and expiration before and after surgery. A semiautomated segmentation method was developed to isolate the lung regions and calculate the lung volumes and frequency distribution of attenuation values. The changes in lung volume and attenuation after surgery were compared with clinical findings, and an exploratory evaluation of outcome predictors was conducted.
Results: Semiautomated segmentation and quantitative analysis compared favorably with manual techniques, and there was good correlation between the emphysema indexes and percentage predicted forced expiratory volume in 1 second, forced expiratory volume in 1 second/forced vital capacity, and diffusing capacity. The emphysema index decreased from 60% to 38% at inspiration and from 60% to 27% at expiration after surgery. The average CT lung volume decreased from 7.5 to 5.6 L at inspiration (25%) and from 6.4 to 3.8 L (41%) at expiration after surgery and correlated well with measurements at plethysmography.
Conclusion: Substantial decreases in the lung volumes and emphysema index, increased airflow, possible reexpansion of some remaining lung, and the relation between preoperative quantitative CT indexes and clinical outcome suggest a multifactorial mechanism for improvement seen after surgery.