[Influence of interest region and interest value settings on exposure index-analysis using chest clinical images]

With the digitization of general radiography, there are some concerns about an increase in radiation exposure doses. Therefore, the exposure index (EI) as a new dose index was proposed in 2008 by IEC. However, the settings for the interest region and the interest value in the clinical image do not show concrete prescribed values. Therefore, we inspected the distribution of EI by changing the interest region and the interest value for a standing-position chest radiograph image in students' medical examinations. EI50f, which is generally used, fluctuated between 41 and 136. In addition, as the area of the interest region became smaller, EI increased and the variation index increased. For the interest value, 50% (EI50h) was smaller than 85% (EI85h), and the variation index was also smaller. EI was not the absolute value in the clinical image, and immediate display of the deviation index (DI) with target exposure index (EIT) was effective of the adequacy of the radiography condition.