Carbon ion radiotherapy and radiographic changes in a typical patient. (A) Pre-treatment CT scan of oligo-recurrence in the lung from colorectal cancer. (B) Radiotherapy plan for oligo-recurrent pulmonary lesion, which received 60 GyE in four fractions. The yellow line indicates the clinical target volume that was delineated in the expiratory phase. Dose distribution is shown with isodose lines of different colors (color scale on left side of image). The clinical target volume is fully encompassed by the 95% isodose line. (C) Chest CT scan 16 months after irradiation, revealing no evidence of recurrence.