2005 年 61 巻 5 号 p. 683-690
The increased clinical use of multi-detector-row CT(MDCT) may result in increased radiation doses for patients. The objective of this study was to compare radiation dose profiles between MDCT with 16 data acquisition systems, MDCT with 4 data acquisition systems, and single-detector-row CT (SDCT), and to compare effective doses among them to measure specific organ doses. When comparing radiation dose profiles on the Z-axis, doses outside the scanning range increased, especially when a 20 mm X-ray beam width was used. Effective doses also were higher with MDCT (low helical pitch) than with SDCT (helical pitch 1.0 : 1), but were not higher with MDCT (high helical pitch) than with SDCT (helical pitch 1.0 : 1). When a 20 mm X-ray beam width or high helical pitch was used, scanning time was shortened, but doses outside the scanning range were increased. When the standard deviation (SD) is the same, there is not much difference between SDCT and MDCT in terms of effective doses if the helical pitch is 1.0 : 1. It can be expected that X-ray over-wrap under low helical pitch and incorrect parameter setting cause increased radiation dose to the patient. Therefore, high helical pitch should be used if it is possible to disregard the influence of image noise. It is important to be cautious in regard to patient radiation dose when MDCT is used, and it is necessary to perform high-quality examinations at as low a dose as possible. Optimization of the scan parameters is an important issue for the future.