Head and abdomen CT exposures in Portugal.

In Portugal, computed tomography (CT) exposures for adult routine head, adult routine abdomen and paediatric abdomen (5 years old) were evaluated between 2019 and 2020 in 92 CT units. The third quartile value for CTDIwas 63.2 mGy for adult head exams, 15.9 mGy for adult abdomen and 5.2 mGy for paediatric abdomen. However, the CTDIfor head examination in 7.6% of units exceeded the suspension level proposed in EU report 162 while the number of units exceeding suspension levels for adult and paediatric abdomen were 3.2% and 0.0%, respectively. The used acquisition parameters and the referred CT unit's specifications were studied to understand how radiation dose relates with tube voltage, tube current, rotation time, detector width, slice width, pitch value and the use of automatic exposure control (AEC). The axial acquisition mode was predominant (67%) in the head exams. However, the helical scanning was commonly used in abdomen exams. Dose reduction from adult to paediatric exams was achieved using a lower tube current (a 60% average reduction). AEC is preferably used in abdomen protocols (84% in adult exams and 96% in paediatric exams). Nonetheless, in adult routine head protocols only 27% used this system. Data was gathered from clinics and hospitals covered by this study which allowed an estimate of an annual frequency of 206 CT examinations per 1000 population in Portugal. The estimated dose index (CTDI) and frequency of CT examinations for the Portuguese population agreed with data from other countries.