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Alignment of imaging and treatment isocenter
Precise alignment of imaging and treatment isocenter is
crucial in image-guided SRS
Ball bearing phantom:
1. Phantom is positioned in the MV-treatment
isocenter
2. Distance or phantom to imaging isocenter is
measured
Accuracies of < 1mm are usually specified
Alignment stable over time (Wiehle et al. 2009)
Verification prior to each single fraction radiosurgery