1. A non-transitory computer-readable storage medium storing instructions which, when executed by a processor, cause a computer to: acquire image data of a patient's chest; generate a set of two-dimensional (2D) slice images based on the acquired image data; determine a seed voxel in a trachea connected to a lung in a first slice image from the set of 2D slice images; apply a region growing process to the first slice image from the set of 2D slice images starting with the seed voxel using a threshold value, wherein a region grown by applying the region growing process corresponds to a lung; generate a set of binarized 2D slice images based on the region grown from the seed voxel; filter out connected components of the lung in each slice image of the set of binarized 2D slice images; and identify the pleural boundaries of the lung based on the set of binarized 2D slice images.