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. Author manuscript; available in PMC: 2013 Jan 21.
Published in final edited form as: Phys Med Biol. 2011 Dec 9;57(2):309–328. doi: 10.1088/0031-9155/57/2/309

Figure 4.

Figure 4

(a) CT image roughness noise vs. CT absorbed radiation dose. (b) PET image roughness noise vs. CT absorbed radiation dose. Results are based on 20 each repeated CT and PET i.i.d. simulations using various filtration and kVp, mAs parameters for a 20 × 30 cm elliptical water-filled phantom. The CT tube current is varied for each kVp from 500 mA down to 0.5 mA leading to different absorbed doses (0.5 s tube rotation time). The CT dose is measured as the mean absorbed dose across the central part of the phantom with slice thickness of 3.125 mm. As illustration, the standard error of the mean is shown as error bar for the 80 kVp no filtration case, but is too small to be observed. For CT, lower range is truncated if bias is over than 700 HU with visually obvious artifacts. For PET, lower range is truncated if corresponding bias is more than 20%.