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Reliability of bony anatomy
If visualization of the target is not possible, one has to use the bony
skull as a surrogate for the actual intra-cranial target in IGRT
However, internal “motion” of intra-cerebral tumor could be caused
by:
• Tumor progression
• Tumor shrinkage
• Changes of peritumoral edema
Set-up prior to treatment was verified based on the
a)
position of the metastasis (soft tissue match): imaging using an in-room CT
scanner after application of iv contrast
b)
position of the bony anatomy (bone match): imaging using cone-beam CT
a
b