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Stereotactic
Irradiation Protocols
Stereotactic
Conformal Radiotherapy (SCRT)
Immobilisation
in BrainLAB mask/frame system
Imaging
- Localisation/planning
CT scan in the frame (Double contrast, 3/3mm in the tumour bearing are
and 5/6mm outside)
- Planning
MRI with 1-3 mm cuts. Contrast enhanced 3DFSPGR axial sequence
only.
- Fusion
of planning CT and MRI on Brain LAB
Target
Delineation
- GTV =
enhancing mass including areas presumed to contain active tumour
Critical structures including eyes, optic nerves/chiasm (and
hypothalamus) and brain stem to be outlined
- CTV
margin = 0 to 5 mm and edited appropriately
- PTV
margin = 2 mm
Planning
technique: 6-8
non-coplanar fields, individually shaped with microMLC of the BrainLAB.
Dose
Prescription: Dose prescribed at isocentre (plans normalised to 100%
at isocentre) with PTV covered by 95% isodose line as per ICRU 50
guidelines
- Pituitary
adenoma 45Gy in 25# in 5 weeks
- Craniopharyngioma
54Gy in 30# in 6 weeks
- Meningioma
and Acoustic neuroma 54Gy in 30# in 6 weeks
- Optic
nerve meningioma 50.4 Gy in 30# in 6 weeks
Trial
Consider
patients between 6-25 years with low-grade glioma, craniopharyngioma and
meningioma for SCRT Trial (conventional vs SCRT).
Stereotactic
Radiosurgery
Common
Indications: Solitary brain metastasis and AVM
Immobilisation
and Imaging: as in SCRT
Target
Delineation
- TGTV
= enhanced lesion
- PTV =
GTV + 2mm in 3D
Planning technique: 6-9 non-coplanar individually conformed fixed
fields
Dose
Prescription
- Solitary brain metastasis
15-20 Gy in single fraction, prescribed at 90-95% isodose (plans
normalised to 100% at isocentre).
- Recurrent high grade glioma
30-35Gy in 6-7 daily fractions
- AVM- assess the suitability
of SRS after discussing in the JNOM. Check size, location and supply
of the lesion. Planning MRI and MRA a few days before actual day of
the procedure. Dose- 12-25 Gy
(individualised).
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