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High-end CT systems allow acquisition of isotropic volumetric data sets that permit high quality reformatted images and images with less than 1 mm slice thickness. These capabilities have greatly expanded the usefulness of CT, and CT usage has correspondingly increased, replacing more and more radiographic examinations. In 1990, approximately 13 million CT scans were performed in the United States. 1 In 2000, the number of CT scans more than tripled to approximately 46 million. 1 The estimated number of CT scans for 2006 is 62 million. 1 With high-quality CT imaging being performed more frequently, patients can benefit from a quicker and more accurate diagnosis and precise anatomic information for planning therapeutic procedures. Despite the tremendous contributions of CT to modern health care, however, some attention must also be given to the small health risk associated with the ionizing …