Investigation of radiation dose and diagnostic reference levels in CT scanning for adult patients

Objective: To understand the CT radiation dose status of adult patients, and to investigate the diagnostic reference levels in adults by a nationwide survey for CT radiation dose. Methods: From Sept 2015 to Mar 2016, 168 hospitals in 30 provinces, autonomous regions and municipalities were surveyed randomly, which included tertiary hospitals and second grade general hospitals with each for about half. 168 CT units with annual qualified state inspection randomly surveyed including brands and models commonly used in clinical applications. The clinical cases were collected for a total of 12 scanning items such as head, sinuses, neck, chest, abdomen, pelvis, lumbar spine, urography, coronary CTA, head CTA, neck CTA, chest and abdomen CTA, with each of 10 random cases. The CTDI_vol and DLP were selected as radiation dose parameters. All data for each item were sorted in accordance with numerical value, and obtained 25th percentile, 50th percentile and 75th percentile (diagnostic reference levels). The resulting dose values were compared with the diagnostic reference levels published by relevant international organizations on radiological protection. Results: A total of 16244 dose values of adult patients with standard body figure were collected and 15970 dose values were left while 274 invalid values removed. For different CT users nationwide, CTDI_vol, DLP and scanning phases were quite different for the same scanning item. Compared with values released by international radiological protection organizations, the degree of difference in the diagnostic reference levels varied for different scanning items. They had similar level in brain scanning and lower levels in chest/abdomen scanning. The items with maximum dose index were head, coronary CTA, head CTA and sinuses. Although CTDI_vol for urography was only 20 mGy, DLP was as high as 2620 mGy·cm. Conclusions: The existing CT dose levels in our country does not accord with the DRLs released by related international organizations, and we should set up our own DRLs according to the clinical reality. (authors)