SCANNING SLIT CHEST RADIOGRAPHY - A PRACTICAL AND EFFICIENT SCATTER CONTROL DESIGN

PURPOSE: To design a chest radiography unit that eliminates scatter. MATERIALS AND METHODS: A scanning slit radiography unit that also incorporates a conventional grid was designed. The scanning slit geometry defined a 10-mm-wide beam at the image receptor. RESULTS: With a typical heavy-duty radiographic tube, the proposed system was capable of delivering an entrance skin exposure of up to 32 mu C/kg for a 1-second scan. Monte Carlo simulations indicated that the scatter-to-primary ratio (S/P) imaged with the scanning slit system alone was 0.125 for a 35 x 43-cm, 23-cm-thick Lucite phantom imaged at 140 kVp. When the system was coupled with 4:1, 8:1, and 12:1 grids, S/P decreased to 0.063, 0.055, and 0.054, respectively. CONCLUSION: A scanning slit system coupled with a conventional grid is a practical and highly efficient method of controlling scatter and will result in minimal soft-tissue and bone measurement errors in dual-energy chest radiography.