COMPARISON OF SCATTER MEASUREMENT TECHNIQUES IN DIGITAL FLUOROSCOPY

A number of slightly different methods of scatter measurement using th e Pb disk technique are described in the literature. These methods are based on applying different forms of data extrapolation to determine the disk-free scatter signal, and it is possible to infer that differe nt results might be obtained. This note reports on an examination of t he technique in digital fluoroscopy, and its comparison with a techniq ue based on the use of a 2.5 mm aperture in a Pb sheet. It was found t hat linear extrapolation of signals generated in the shadows of Pb dis ks of diameter 1 mm to 5 mm, with disk diameter as the independent var iable, gave a scatter-to-primary ratio (SPR) estimate which was within 1% of that provided by the aperture technique. It was also found that linear extrapolation, with disk area as the independent variable, gav e an SPR estimate 8.6% lower than the aperture technique for disks of diameter 1 mm to 5 mm, and 42% lower for disks of diameter 1 cm to 6 c m.