1. Mass Screening With CT Colonography: Should the Radiation Exposure Be of Concern? 
David J. Brenner, Maria A. Georgsson 
Gastroenterology 
Volume 129, Issue 1, Pages (July 2005)
DOI: /j.gastro
Copyright © 2005 American Gastroenterological Association Terms and Conditions

2. Figure 1
Number of articles listed in PubMed (Medline) on CTC or virtual colonoscopy.
Gastroenterology  , DOI: ( /j.gastro )
Copyright © 2005 American Gastroenterological Association Terms and Conditions

3. Figure 2
Excellent radiologic contrast between a soft-tissue polyp and the air-filled lumen, with or without cathartic preparation. Two-dimensional transverse images are shown here from extremely low-dose CTC examinations.8,36 The scanner settings used here (Siemens Plus 4 Volume Zoom, Erlangen, Germany; 9 mAs; pitch, .9; collimation, 4 × 2.5 mm; 140 kV) result in doses less than one fourth of the currently typical values tabulated in Table 2. (A) A 9-mm sessile polyp imaged in a cathartically prepared colon (arrow).36 (B) CTC without cathartic preparation.8 Liquid fecal material is tagged homogeneously (arrowhead); 8-mm polyp (long arrow); 20-mm polyp identified while completely submerged in liquid fecal material (short arrow). Reproduced courtesy of Dr. Riccardo Iannaccone, University of Rome.
Gastroenterology  , DOI: ( /j.gastro )
Copyright © 2005 American Gastroenterological Association Terms and Conditions

4. Figure 3
Estimated radiation-related absolute cancer mortality risk/105 individuals in the United States exposed at different ages to a whole-body dose of 10 mSv. Estimates from the 1990 NAS BEIR-V report.46
Gastroenterology  , DOI: ( /j.gastro )
Copyright © 2005 American Gastroenterological Association Terms and Conditions

5. Figure 4
Sources of ionizing radiation exposure (technically the collective effective dose) to an average individual in the United States. The difference in the contribution of medical x-rays between and 2000 is caused primarily by the increase in CT scans—from about 2 million per year in 1980 to about 58 million in
Gastroenterology  , DOI: ( /j.gastro )
Copyright © 2005 American Gastroenterological Association Terms and Conditions

6. Figure 5
Helical (spiral) CT scanning. Both the x-ray source and, on the other side of the patient, the x-ray detectors, rotate around the patient. If the table were not moving, a single slice of the patient would be imaged (axial CT). Because the table is moving at the same speed as the source-detector combination is rotating, the result is a helical or spiral CT scan of the patient, as depicted here. A single row of detectors is shown; modern multidetector scanners have several rows of detectors alongside each other, which allow both for thinner slice widths and shorter scan times.
Gastroenterology  , DOI: ( /j.gastro )
Copyright © 2005 American Gastroenterological Association Terms and Conditions

7. Figure 6
Principles of automatic tube current modulation. (A) Angular modulation in which the x-ray tube current is lowered as the x-rays are aimed in the anteroposterior directions, and increased when the x-rays are aimed in the lateral-medial directions, when there will be more x-ray attenuation. (B) Z-axis modulation in which, for example, fewer x-rays are required in the abdominal region superior to the pelvic bones compared with the pelvic region.
Gastroenterology  , DOI: ( /j.gastro )
Copyright © 2005 American Gastroenterological Association Terms and Conditions

8. Figure 7
Idealized computer representation of internal organs used in ImPACT calculations39 of organ doses from CTC examinations. Shaded area indicates scanning region for CTC assumed in this study.
Gastroenterology  , DOI: ( /j.gastro )
Copyright © 2005 American Gastroenterological Association Terms and Conditions