[Simulations of bronchial displacement owing to solitary pulmonary nodules]

On the basis of elasticity dynamics, we constructed mathematical models of bronchial displacements caused by well-differentiated adenocarcinoma and inflammatory pulmonary nodules. We simulated bronchial displacement with a three-dimensional model of the airway tree that we constructed. One-hundred sixty simulations of cancerous and inflammatory displacements were performed, where 20 nodule centers were placed in the right upper lobe in the three-dimensional bronchial model and four different sizes (30 mm, 37.5 mm, 45 mm, and 60 mm) of original lesions were assumed which contracted to nodules of 15 mm in diameter. The three-dimensional simulation images were highly similar to the cancerous or inflammatory nodules in the clinical images. Angles and distances in simulated structures between respective branches and the nodule center were measured. The mean value of angles of branches whose distance from the nodule center was within a range of 6 mm to 12 mm was in good accordance with the value obtained theoretically. Discrimination between cancer and inflammation was successfully carried out by examining the distance dependency of the angles. We concluded that the measurement of angles of linear structures surrounding a pulmonary nodule would be useful for its differential diagnosis.