Fig. 7.

A The set-up used for acquiring scatter measurements with a 30- × 30- × 20-cm solid water block at various gantry angles is shown here. A 75-cc ion chamber is fixed to a moveable lead shield for support, and a 6-cc ion chamber is placed underneath the table for measuring the table entrance exposure. B The same set-up is repeated with fixed gantry orientation (AP), whereas the chamber is moved at 10 cm intervals along a line which is 80 cm from the phantom centerline and parallel to the longitudinal axis of the catheterization table. C The setup used for measuring scatter dose with no shift along the longitudinal axis of the table, while the chamber is moved in a transverse direction at 10 cm intervals