A medical system including a medical device having an outer diameter, a display device, and a controller. The controller is configured to acquire data regarding a biological lumen such as an airway structure, acquire an image of the airway structure, generate an overlay representing the outer diameter of the medical device, and display, on the display device, the overlay representing the outer diameter of the medical device on the acquired image of the airway structure. The overlay is scaled relative to a diameter of the airway structure at a focal plane of the airway structure based on the acquired data.