| SRS Planning Treatment Volumes (PTVs) | Description of margins |
| Ant PTV1 | PTV itself |
| Ant PTV2 | 1 mm margin from “antPTV1” |
| Ant PTV3 | 2 mm margin from “antPTV1” |
| Post PTV1 | PTV itself |
| Post PTV2 | 1 mm margin from “postPTV1” |
| Post PTV3 | 2 mm posterior from “brainstem” |
| Post PTV4 | 4 mm posterior from “brainstem” |
| Post PTV5 | 6 mm posterior from “brainstem” |