Daniel J. Staton, PhD
A past operating mode in CT was to focus on image quality with less emphasis on limiting CT dose. This may have been practical dur-ing the days of single-slice scanners, when tube heating helped serve as a limiting factor in administering radiation dose. With the advent of complex, multislice systems that have tube heating capacities capable of delivering radiation doses sufficient to cause deterministic effects in patients, there is increasing awareness of limiting CT dose to patients. In the United States, recently reported incidents with radiation overexposures during CT ex-aminations have sparked nationwide attention to CT dose and new policies and regulations. Previous incidents of CT overexposures in Japan were reported [1]. Protocols in CT scanners directly affect (control) radiation dose to patients as well as all of the technical factors for image acquisition and reconstruction. There are several clinical issues regarding CT protocols: