11) Whole brain irradiation

1) Positioning / immobilization for WBI

-supine

-headrest F

-arm to side

-triangle foam (knee)

-tape (clinical markup); aquaplast (shell)

What is the TDF for whole brain irradiation?

-20Gy 5# - 1 week

-30Gy 10% - 2 weeks

2) Localization

CT sim = GTV/PTV/CTV

Clinical mark-up
- measure head sep. via calliper
- calculate tx time
- enter data into record/verify system

What are the limitations of CLINICAL MARKUP for brain?

might miss small vol of brain @ cribiform plate (leukemia, lymphoma, medulloblastoma)

If we think we need to include this area → use shell + CT sim + MLC to the eye orbit + face

Why might we use whole brain irradiation?

1) prevent bone metastases (secondary tumors)

2) prophylactically
- CT can’t cross BB so we use radiation therapy (adjuvant to CT)