Abstract: Disclosed are systems, devices, and methods for marking a main carina and a trachea of a patient, an exemplary method comprising importing slice images of a chest of the patient, generating a three-dimensional (3D) model based on the imported slice images, displaying the 3D model in a graphical user interface (GUI), locating the main carina by viewing 2D images of the 3D model in an axial orientation, marking the main carina in one of the 2D images of the 3D model, adjusting a view plane of the 3D model around a rotation axis defined by the marked location of the main carina to adjust the view plane from an axial orientation to a coronal orientation while keeping the main carina in the view plane to thereby display the entire trachea on the GUI, and marking an upper end of the trachea in one of the 2D images of the 3D model.