Figure 4.

RT Plan for Carcinoma of the Left Tonsil

Coronal and axial views of the radiation therapy (RT) plan used to treat a human papillomavirus–positive carcinoma of the left tonsil metastatic to the left neck lymph nodes (blue shaded region) in a 44-year-old woman. Isodose lines, in Gray (Gy), represent the dose distribution similar to topographical lines on a map. This patient was prescribed 70 Gy in 35 treatments to gross tumor (red line), with an intermediate-dose region of 63 Gy (green line) and a low-dose region of 56 Gy to the at-risk lymphatics (magenta line). One can appreciate the high radiation exposure to the carotid vessels, including the carotid bulb (red arrow).