342-343 / 2437
isocentre
tumour
Spinal canal
rotation of collimator
according to divergence
angle of upper spinal field
SSD : source to skin distance
SSD
100 cm
SSD
100 cm
moving junction
Junction lines are moved 0.5-1.0 cm every 8-12 Gy
to avoid overdosing or underdosing segments of the cord
Procedure:
1. shortening the inferior margin of the lateral cranial fields
2. Symmetrically lengthening the superior and inferior margins
of the posterior spine field
3. Shortening the cranail margin of the caudal spinal field
4. The caudal spinal field remains unchanged
Technical Procedure