Change in Exposure Index According to the Subject and Foreign Body Movement of Position

摘要

In most of the Digital Radiology Equipment, they have the system to provide exposure information to the inspector, and call this Exposure Index. EI can be classified as ROI Based EI and Histogram EI. We tried to see the change of EI according to the place of foreign body and subject in the detector, having chest PA inspection condition as the center. The first experiment method is to see the change of EI according to the movement of subject. Second method is the comparison of EI according to the foreign body movement by the set-up of EI. The third method is to compare and evaluate EI by the set-up ways of EI and the movement of shielding material. By the result of movement of the subject, for ROI based EI left and right, for Histogram EI middle and down, and in left and right had the same EI. By the result of movement of foreign matter, in the other 4 sectors, there were no changes in ROI Based EI and Histogram EI, and it was same for the each sectors. By the result of movement of the shield, ROI based EI, when Pb Protector was in the place of 14~20cm, the EI was same as the standard. Histogram EI Pb Protector Place was in 2~20cm, EI was 500, which is the same with the standard. In the same condition, by the EI set up method, the patient position and foreign body changed the quality of image by the position, and this shows that ROI based EI has big influence in Subject and Foreign Body Detector by the place and size. However Histogram EI can provide steady image because it doesn't get influenced by such environment.