Abstract: To comprehensively know well the frequency of CT application and distribution characteristics of examinees in Hongkou District, Shanghai city, and to provide data support for further improving medical radiation protection and guiding the rational application of CT examination, a survey method was used to create a unified survey form. The CT examination items included 8 examination positions, including head, chest, abdomen, spine, pelvis, limbs, CT intervention, and others. According to the age group division method proposed by UNSCEAR, they were divided into 3 age groups: less than and equal to 16 years old, 16-40 years old, and over 40 years old. The survey data will be firstly obtained from the medical institution information system for the number of CT examinations from October 1, 2022 to September 30, 2023. Secondly, manual recording will be selected and further statistics will be filled in the survey form. Excel software will be used to summarize and analyze the data. A total of 11 medical institutions in Hongkou District conducted CT examinations, including 3 class-A hospitals, 4 secondary hospitals, 1 primary hospital, and 3 unclassified hospitals. There were 27 CT devices and 39.3 CT scans per million population. In 2023, the total number of CT scans was 934 653, with an annual application frequency of 1 359 person times per thousand population. The most commonly used scanning area was the chest, accounting for 57.20%, with the top five scanning areas totally accounting for 94.40%. The overall male to female ratio of CT scans in 2023 was 0.96∶1, with slightly more female examinees than male examinees in the main types of examinations such as head, chest, abdomen, spine, and limbs. All types of examinations showed that the total proportion of examinees over 40 years old accounted for 82.19%. In 2023, CT scans in Hongkou District were mainly conducted in secondary and class-A hospitals, with the majority of examinees being over 40 years old, slightly more female than male examinees. The frequency of application has increased by 4.5 times compared to the application frequency of 304 person times per thousand population in Shanghai in 2016. Therefore, it is particularly important to strengthen the justification assessment and protection optimization of CT examinations to reduce unnecessary radiation exposure risk.

Key words: X-ray CT, application frequency, distribution characteristics, Hongkou District