Knowledge-based segmentation of thoracic computed tomography images for assessment of split lung function

The assessment of differential left and right lung function is important fo r patients under consideration for lung resection procedures such as single lung transplantation. We developed an automated, knowledge-based segmentat ion algorithm for purposes of deriving functional information from dynamic computed tomography (CT) image data. Median lung attenuation (HU) and area measurements were automatically calculated for each lung from thoracic CT i mages acquired during a forced expiratory maneuver as indicators of the amo unt and rate of airflow. The accuracy of these derived measures from fully automated segmentation was validated against those from segmentation using manual editing by an expert observer. A total of 1313 axial images were ana lyzed from 49 patients. The images were segmented using our knowledge-based system that identifies the chest wall, mediastinum, trachea, large airways and lung parenchyma on CT images. The key components of the system are an anatomical model, an inference engine and image processing routines, and se gmentation involves matching objects extracted from the image to anatomical objects described in the model. The segmentation results from all images w ere inspected by the expert observer. Manual editing was required to correc t 183 (13.94%) of the images, and the sensitivity, specificity, and accurac y of the knowledge-based segmentation were greater than 98.55% in classifyi ng pixels as lung or nonlung. There was no significant difference between m edian lung attenuation or area values from automated and edited segmentatio ns (p > 0.70). Using the knowledge-based segmentation method we can automat ically derive indirect quantitative measures of single lung function that c annot be obtained using conventional pulmonary function tests. (C) 2000 Ame rican Association of Physicists in Medicine. [S0094-2405(00)01703-X].