2017_IGRT course book

Can there be a good external surrogate for the position of a lung/liver tumour?

• No surrogate is good enough

• Solution 1: use large margins ( approx equal to free breathing)

• Solution 2: image the tumour position daily with respiration- correlated (4D) IGRT ➢ 4D-CBCT for gated treatment ➢ Breath hold CBCT ➢ 2D + markers in the tumour