Surface monitoring procedure ―The procedure is expected to last approximately 15 minutes after the end of the 4DCT scan, which is the standard-of-care for lung SBRT treatments at our institution. The procedure will consist of real-time surface tracking using the VisionRT system of the thoracic and/or abdominal region. Continuous audiovisual contact will be maintained with the subject during scanning. Each individual will be informed that they can stop the procedure at any point.