Figure 1.

(a) The geometry of the computer simulations is shown. PMMA, polyethylene, and water were used as phantom compositions. The simulations included the head and body bow tie filters, as well is no bow tie filter. Dose was computed at the center of the cylinder, at the edge, and over the entire 10-mm-thick slab of the cylinder as well. (b) The x, y, z coordinate system typically used in CT is illustrated. The doses computed in this research involved the smooth rotation of the x-ray source 2π around the cylinder, with no advancement along the z axis. The locations of the center, edge, and entire CT volumes for dose computation are shown, and in each case these cylindrical volumes were 10 mm long in the z dimension.