Several surveys on medical exposure have been performed in provinces across the countries over the past decades[7–13]. Most of these surveys were completed by means of sampling survey methods. A sample survey in Shanghai [14] in 2016 indicated that the frequencies of X-ray examinations and CT scans were 812 and 304 per 1,000 population, respectively. A similar study in Guangdong indicated that the frequencies of X-ray examinations and CT scans of 699 and 293 per 1,000 population, respectively [15]. A survey in Heilongjiang was performed across the whole province, with the frequencies of 201 and 184 per 1000 population, respectively, for these two categories of examinations [16].
A sample survey completed in 2015 in four counties in the province showed that the frequencies of X-ray examinations and CT scans were 303 and 175 per 1,000 population, respectively [3]. In the same year, a resource survey showed that there were18,639 radiological staff and 9,355 pieces of radiological equipment in the province, including 946 CT scanners [17]. The survey in 2016 indicated that the frequency of radiodiagnosis (including conventional radiodiagnosis, CT scans and other diagnosis) was 911 per 1,000 population, including 239 CT scans per 1,000 [4]. Moreover, the survey also showed that there were 9,248 pieces of X-ray diagnostic equipment in 2016, including 1,110 CT scanners [4]. The present survey results showed that the frequencies of procedures carried out in 2019 were 452 X-ray examinations and 297 CT scans per 1,000 population. The province had a total of 9,314 radiodiagnosistic units (excluding those for use in dental clinics), including 1,759 CT scanners. The results showed there was a total of 27,188 radiological staff in the province.
Although slightly different in surveys above-mentioned, it is clear that both the application and equipment of X-ray examination have recently had a rapid increase in the province. Number of CT scanners increased by 56% and frequency of CT scans by 31%, respectively. Number of CT examinations was higher than that of CT scanners, suggesting that CT scanning was in short supply lately. Some surveys abroad showed similar trend. Two surveys conducted in 2013 and 2018in Swiss showed that the CT scanning frequency increased by about 13% from 117 per 1000 population to 132 per 1000 over the five years [18, 19].
Although a linear relationship between radiodiagnosis frequency and GDP per capita was observed in the 2017 survey [5], the correlation was not strong (R2 is 0.507 for conventional X-ray and 0.306 for CT). Therefore, the present study focused on the relationship between GDP, medical resources indicators such as number of beds, outpatients, staff and the number of examinations. The number of two categories of examinations and economic and health indicators in the prefecture-level cities was displayed inTable3.The correlation factors displayed in Table 4.
These results above suggested the cities or regions with larger economic scale would have more diagnostic examinations for following reasons. First, the cities with larger economic scale would have more medical resources including both the hardware represented by numbers of beds and the human resources represented by medical staff numbers. Second, larger economic scale cities could afford more medical practices represented by outpatient numbers, leading to more radiodiagnostic procedures.
In order to observe the correlation between economic development and radiodiagnostic exposure frequency, the population factors were excluded and a correlation analysis was performed between examination frequency and some economic indicators, such as per capita GDP, with analytical results displayed in Table 6. These correlation factors indicated that the economic development still has an impact on geographic distribution of medical X-ray examination although the population factor was excluded.
Although the results of present survey reflect the geographic distribution of diagnostic medical exposure, it would be not proper to conclude that the examination frequency would increase with GDP. The reason is that the application of examination could be influenced by the shifting of some other factors, such as local health policy, medical budget, and replacement of conventional technology of which a good example is the replacement of conventional X-ray examination with CT scans.
In 2015, a study based on the data of European Commission project “DOSE DATAMED 2 (DDM2)” analyzed the factors correlating with medical radiological examination frequencies[20]. The results of the study suggested that the high income countries appear to perform more CT scans while X-ray examination does not exhibit similar trend. This difference may originate from the other factors affecting examination frequency. These factors mentioned in the present paper could be health care spending (%), reimbursement, etc. One advantage of the present survey is that these factors mentioned above in 13 cities are closed and the effect of these factors was excluded. Thus the results of this study made a better answer to the hypothesis of the study at city level.
The finding of present survey provided a new scale up strategy in cluster sample survey on frequency at the province or city level. That means in a cluster sample survey, by surveying some typical regions (or cities) X-ray examination number, the number of the population could be estimated by scaling up with GDP. The choices in previous study were to scale up on the basis of population [21], X-ray unit quantity[22–23], and outpatient amount [24].
There are some limitations in the present survey. Firstly, the number of beds, outpatients and technicians of each institution was not surveyed. Thus, the relationship between the number of examinations and these factors was not analyzed at the hospital level. Secondly, this survey did not include dental clinics, resulting in the inability to estimate the frequency of dental radiography. Thirdly, since the survey subjects do not include dental clinics, the statistics on dental radiology equipment are limited to the equipment in hospitals and are thus incomplete in the province. Lastly, the information about radiodiagnosis mostly came from the RIS of the institutions, and the radiodiagnosis (such as radiodiagnosis from operating room, ultrasonic lithotrite and other equipment), which is not connected to the Radiology Information System (RIS), was not included in the statistical scope.
The present study surveyed the numbers of radiodiagnostic equipment and examination of the province in 2019. Also the general province wide frequencies of medical X-ray examinations of two types were estimated. Through correlation analysis, the influencing factors of radiodiagnosis frequency were observed at the two levels of medical institutions and cities. The present study provided a basis for improving the survey method on radiodiagnosis province wide and even countrywide. In the future, on the basis of the present study, the following actions may be taken, to continue assessment of the frequency of the radiodiagnosis and following the influence of the COVID-19 pandemic. ② expanding the scope of the survey to include dental clinics; ③expanding the survey scope to estimate the province wide and even countrywide frequencies of radiodiagnosis; ④Combined with the dose research on various forms of radiodiagnosis, the results of the present study could be utilized to evaluate the risk of radiodiagnosis procedure in the province.