the trial required field placement to within 3mm. radiographers from participating centres related set-up methods to accuracy to establish best practice and inform recommendations. all centres made changes to methods as a result of the trial to improve accuracy, identified in categories, including patient positioning, iso-centre setting, couch top, imaging methods, and bladder and rectal filling. up to 80% of centres made changes in any one category.

in three centres accuracy was inferior in one axis, related to the set-up methods used.

recommendations included:

1. for reproducibility –

1. achieving a comfortable bladder status

2. using a standardised firm head support (not pillow)

3. using the hands on chest position to avoid the weight of the arms on the trunk

4. aligning lateral tattoos in both the longitudinal and vertical directions

5. using leg or ankle supports

evidence-based methods of controlling rectal filling are still required

1. for iso-centre setting –

1. using the anterior tattoo for lateral direction and the lateral tattoos for the superior/inferior direction

2. using a solid/carbon couch top throughout, using the height above couch as the reference measurement, not the anterior source to skin distance

3. develop an alternative to using the couch height readout alone