Figure 6a. Image noise in a 70-year-old asymptomatic man. (a) Three-dimensional endoluminal CT image (50 mAs) shows a smooth bowel wall with a 10-mm polyp (arrow). (b) Three-dimensional endoluminal CT image (10 mAs) shows the bowel wall with a continuous granular-nodular surface pattern due to increasing noise. Note that the polyp (arrow) is still visible with the decreased dose.