List in order of increasing reproducibility, the various setup/immobilisation techniques and devices used on your linac.
The reproducibility of treatment is dependent on the degree of immobilisation. Treatments which have less reproducibility have a higher tolerance, and this reduction in accuracy is compensated for by an enlargement of the planning target volume (PTV).
Breast board (1 cm tolerance)
Vacbag immobilisation (7 mm tolerance)
Prostate treatments - using wingboard, kneefix, footfix with indexing (5 mm tolerance)
Thermoplastic mask (3 mm tolerance)
Stereotactic immobilisation (1 mm tolerance)