Abstract
Purpose: To estimate the annual effective dose per person in Gunma Prefecture by calculating average effective dose from computed tomography (CT) examinations in the area.
Methods: We collected data on age, gender, anatomical region, and dose-length product (DLP) on patients who underwent CT examinations during a specific two-week period in July 2016 from 95 facilities in Gunma Prefecture.
Result: We used data from 12,878 (7,014 males; 5,864 females) CT examinations on patients 10 years old and older (age 66.9+/-17.5 years, 10-104 years). The effective doses were 2.4 mSv for head examinations (2,664 cases), 9.3 mSv for chest examinations (2,192 cases), 19.9 mSv for chest and abdomen examinations (3,906 cases), 16.5 mSv for abdomen examinations (1,611 cases), 14.5 mSv for coronary artery CT examinations (retrospective) (144 cases), 8.6 mSv for coronary artery CT examinations (prospective) (129 cases), 34.2 mSv for dynamic liver examinations (749 cases), with an average of 13.5 mSv overall. According to the National Database (from April, 2016 to March, 2017) of the Ministry of Health, Labour and Welfare, the annual number of CT examinations in Gunma prefecture was 430,000; thus the annual effective dose by CT examination per resident was calculated as 2.95 mSv.
Conclusion: The effective dose per CT examination was 13.5 mSv. The annual effective dose per resident increased by about 28% from that of 2.3 mSv in 2000.
