흉부 CT검사시 AEC Program 적용에 의한 선량감소효과에 관한 연구

Dose Reduction Effect with Automatic Exposure Control Program in Chest CT

Purpose The purpose of this study is to check how much a radiation dose of the thoraxis reduced when using AEC technique in CT examination, and to apply the program properly to clinical cases. Materials and Methods We measured organ doses of thyroid, upper chest, mid chest, lower chest, breast, liver when conducting a test by using Brilliance CT made by Philips, instead of AEC program, and compared the radiation dose reduction effect of each organ by measuring the effect shown when using D-DOM (a method of controlling a tube current according to the thickness of a subject for photography toward X-Y axis of a revolving angle of a tube) among AEC programs, and Z-DOM(a method of controlling a tube current according to the thickness of Z-axis position). Results The comparison between dose with AEC program and dose without AEC program in chest routine CT were as follows, 1. The thyroid dose using D-DOM and Z-DOM wasreduced 23.9% and 49.5% respectively rather than dose of non-AEC program. 2. The upper chest dose using D-DOM and Z-DOM was reduced 18.3% and 17.8% respectively rather than dose of non-AEC program. and The mid. chestdose using D-DOM and Z-DOM was reduced 15.2% and 12.7% respectively rather than dose of non-AEC program. and The lower chest dose using D-DOM and Z-DOM was reduced 5.8% and 22.4% respectively rather than dose of non-AEC program. 3. The breast dose using D-DOM and Z-DOM was reduced 10.7% and 7.5% respectively rather than dose of non-AEC program. 4. The liver dose using D-DOM and Z-DOM was reduced 20.3% and 26.4% respectively rather than dose of non-AEC program. 5. It was proven that as for the radiation dose reduction effect by D-DOM, the control of a tube current was mostly performed in the asymmetrical part such as shoulder when comparing upper chest (18.3%), mid. Chest(15.2%), and lower chest(5.8%). 6. Thyroid, Lower chest showed a greater radiation dose reduction effect when using Z-DOM rather than D-DOM. Conclusion The radiation dose reduction effect in each organ was proven higher by far when using AEC program. In particular, D-DOM demonstrated an excellent radiation dose reduction effect in the part that showed a great difference of thickness between AP and Lateral(ex. shoulder). Z-DOM displayed an outstanding effect in the neck part.