A method for detecting and analyzing emphysema from 3D chest CT images

This paper describes a method for detecting and analyzing emphysema from 3D chest CT images Since emphysema looks low attenuation area (LAA) on CT images, methods for extracting LAA regions from CT images have been reported. However, the intensity of the lung parenchyma changes because the blood pressure varies due to the gravity. Therefore, CT value correction is indespensable in the LAA extraction process. We propose a CT value correction method based on curve fitting that approximates distribution of CT values of the lung. After correction, LAA regions are extracted from the corrected CT images. The proposed method was applied to fourteen cases of 3D chest CT images. It improved LAA extraction results for eight cases. Also, we analyzed the relation between LAA% (rate of LAAs over the lung area) and the pulmonary function test data. The results showed that FEV1 (forced expiratory volume in one second) and RV/TLC (RV: residual volume, TLC: total lung capacity) strongly correlated to LAA%. In addition, the experimental result showed that LAA% of lower parts of the lung showed strong correlation to pulmonary function test data than that of upper parts. These results are consistent with clinical findings.