CT scan, sagittal slice, teletherapy, dog

Sagittal slice CT scan radiation dose color wash of a canine patient affected with recurrent perianal mast cell tumor (yellow star) that has metastasized to the inguinal (black star) and sublumbar lymph nodes (black arrow). At staging, an adrenal tumor was also found (yellow arrow). All of the abnormalities were treated with palliative radiation therapy (4 Gy/fraction on 5 consecutive weekdays). The red areas represent radiation dose at or slightly exceeding the prescription of 20 Gy. The green areas represent radiation dose of approximately 10 Gy, and the blue areas are doses of 1–2 Gy.

The figure demonstrates how teletherapy with a linear accelerator can target multiple lesions throughout the body. Before each treatment, a cone beam CT scan was acquired of the anatomy of interest, and the beam was aligned with the correct target. The patient developed minimal adverse effects despite multiple organs at risk from radiation therapy. The treatment plan shown was performed using intensity-modulated radiation therapy to sculpt the dose to the affected areas while avoiding normal tissues as much as possible.