Increasing radiation doses from modern CT scanners in obese and overweight patients

Purpose: To study if the number of CT exams with a dose of 50 mSv per exam or more has increased or decreased during the past 10 years and study the reasons thereof.

Methods/Materials: The data for 2013-2022 at a tertiary care hospital was analyzed to assess temporal trends in effective dose as estimated automatically by the dose management system (Radimetrics). Using body mass index (BMI), patients were classified into underweight, normal weight, overweight and obese, and dose correlation studied. All CT imaging protocols that led to 50 mSv+ exams were identified. Stratified analysis was performed for diagnostic and interventional CT exams, according to procedure types, patient age groups, imaged body regions, and CT protocols.

Results: A total of 1,353,168 consecutive CTs were performed on 381,790 patients in 10 years. Of these, 6250 CT (0.46%) had 50mSv dose (median 61.4mSv; IQR 55-74mSv). There was an exponential increase in the percentage of 50 mSv+ exams for every age group (from 0-20 to 80+ years). The upward trend started in 2018, with an overall 351% increase from 2017 to 2022, and accounted for 0.67-0.86% exams per year with  50 mSv. In the 4991 CT subset with available BMI, nearly 80% of patients were overweight or obese. Incorporation of newer scanners with powerful x-ray tubes without user-set maximum x-ray output limits likely resulted in the increase during 2018-2022 in 50 mSv+ exams for overweight/obese patients. While there was 3.36 times increase in underweight/normal BMI patients, there was 6 times increase in overweight and obese. The protocols with the highest frequencies (in decreasing order) were: Abdominal Biopsy, Gated Aorta CT/CTA, TAVI/TAVR, Cardiac CTA, Aortic CT/CTA, Head & Neck CT/CTA, Abdomen Pelvis CT/CTA.

Conclusions: There was an exponential increase in proportion of CT exams with >50 mSv dose in recent years likely stemming from use of more powerful CT scanners and a lack of user-prescribed limit on scan phases and tube current/potential/CTDIvol/DLP.
Clinical Implications: Automation and innovations in CT technology requires careful setting of radiation dose levels, particularly for overweight and obese patients, to avoid unnecessary increase in radiation doses.