Plain standard erect posterior anterior chest radiographs were taken for each subject and control, using conventional
exposure of between 60 and 80 kV without an absorption grid. The focal film distance was fixed at 3 m, with centering point between the fourth or fifth thoracic vertebra.Exposures were obtained at full suspended inspiration with elbows flexed, back of hands placed on hips, and elbows pushed gently forwards. Exposure time was between 0–05 and
0–08 s.