Esophagus and spinal cord motion relative to GTV motion in four-dimensional CTs of lung cancer patients

Respiration-related variations in the distance between the center of mass of gross tumor volume and both esophagus and spinal cord in the transversal plane were on average 3 mm (range 1–10 mm) and 2 mm (range 1–5 mm), respectively. Depending on the tumor location and treatment technique, variations might become important for treatment planning.