Physics Bucharest 2017

Limitations of 2D Verification

• Measurement of set-up errors is subjective depending on the quality of the reference compared with the portal image.

• Without markers, only bony anatomy is available as a surrogate for the tumour or target volume.

• Awareness of tumour motion, changes in target volume, proximity of surrounding OARs to the high-dose region, and the impact of patient weight-loss is very limited.

• Portal images are often restricted by treatment field orientation. The alternative is the labour-intensive production of imaging-only fields.