Which combination of exposure factors will most likely contribute to producing the longest-scale contrast?
Film-Screen Grid Field
mAs kVp System Ratio Size
(A) 10 70 400 5:1 14 x 17 inches
(B) 12 90 200 8:1 14 x 17 inches
(C) 15 90 200 12:1 8 x 10 inches
(D) 20 80 400 10:1 11 x 14 inches
Group B. Review the groups of factors. First, because mAs has no effect on the scale of contrast produced, eliminate mAs from consideration by drawing a line through the column. Then, check the two entries in each column that are most likely to produce long-scale contrast. For example, in the kVp column, because higher kVp will produce longer-scale contrast, place check marks next to each 90 kVp. In the film-screen column, the slower screens (200) will produce lower (longer scale) contrast than the faster screens; place a check mark next to each. Because lower ratio grids permit a larger quantity of scattered radiation to reach the IR, the 5:1 and 8:1 grids will produce a longer scale of contrast than the higher ratio grids; check them. As the volume of irradiated tissue increases, so does the amount of scattered radiation produced and, consequently, the longer the scale of radiographic contrast; therefore, check the 14 x 17-inch field sizes. An overview shows that the factors in groups A and C have two check marks, whereas the factors in group B have four check marks, indicating that group B will produce the longest-scale contrast.