Three scenarios of the relation between mediastinal disease and the heart. (A) Showing how to use the takeoff of the left main stem coronary artery (outlined in pink) to determine the upper and lower mediastinal locations. (B) Scenario 1: coronal CT images of a 28-year-old man with primary mediastinal lymphoma before (i) and after (ii) 6 cycles of rituximab, cyclophosphamide, doxorubicin, vincristine, prednisone (RCHOP) chemotherapy presenting for consolidation with radiation. (Biii) Axial, coronal, and sagittal views of an IMRT plan (upper panels) and a proton plan (lower panels). (Biv) Corresponding mean doses to critical structures using IMRT vs protons. (C) Scenario 2: coronal CT images of a 25-year-old man with Hodgkin lymphoma before (i) and after (ii) 4 cycles of doxorubicin, bleomycin, vinblastine, and dacarbazine (ABVD) chemotherapy presenting for consolidation with radiation. (Ciii) Axial, coronal, and sagittal views of an IMRT plan (upper panels) and a proton plan (lower panels). (Civ) Corresponding mean doses to critical structures using IMRT vs protons. (D) Scenario 3: coronal CT images of a 30-year-old man with recurrent Hodgkin lymphoma as shown in the coronal images of a PET/CT scan (i-ii) presenting for definitive radiation. (Diii) Axial, coronal, and sagittal views of an IMRT plan (upper panels) and a proton plan (lower panels). (Div) Corresponding mean doses to critical structures using IMRT vs protons.