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Figure 2 (A) The relationship between exposure rate (R/min) and spatial resolution (line pair [lp]/mm) under simulated medium patient habitus conditions. The dark vertical and horizontal lines define the median and average exposure rate and spatial resolution, respectively. The X-ray systems in Quadrant III are exposing patients to excessive radiation with inferior image quality, whereas systems in Quadrant I are obtaining improved image quality at lesser exposures. (B) The relationship between exposure rate and spatial resolution under simulated large patient habitus conditions. To facilitate comparison with Figure 2A, the dark vertical line defines the median exposure rate under these latter conditions, and the dark horizontal line corresponds to an average spatial resolution of 2.2 lp/mm. The risk-benefit ratio is altered compared with that in Figure 2A, with more X-ray systems operating at higher exposures and inferior image quality.