Table 1 Inclusion and exclusion criteria for deeming an image of sufficient quality for reading

Postero-anterior film

Artefacts obscuring the view of the lung fields

A full view of lung fields – the whole thorax with the first rib, lateral ribs and costophrenic angles in view

Images acquired more than 4 weeks prior to pretreatment visit or more than 3 weeks after this

Adequate penetration of film to allow ribs and lung parenchyma to be distinguished