Purpose To assess radiation doses in chest CT exams of different body mass index (BMI), adult patients with COVID-19 infection and to compare them with European CT dose reference levels (DRL). Learning objective To understand how BMI-specific DRL for chest CT in Brazil compare with European DRL and how they could help reduce radiation doses.

Background The WHO recommends judicious and optimized use of CT to reduce radiation doses [1]. Radiation dose optimization not only helps maintain a diagnostic quality CT but also helps avoid excessive radiation doses and reduce concerns over potential harmful effects of radiation exposure in patients undergoing CT [2,3]. Radiation doses with CT can be optimized with use of scanners with efficient detectors and dose optimization technologies such as automatic exposure control (AEC), automatic tube potential selection techniques, and 3D-camera based patient centering, as well as...

Results The median of CTDIvol/DLP values in patients with standard, overweight, and obese BMI were 5.7/211.3, 6.9/257.0, 10.0/339.9 mGy/mGy.cm and 7.6/296.9, 8.9/339.6, 12.3/485.0 mGy/mGy.cm in female and male patients, respectively. There were significant statistical differences between median doses across different BMI classes (p<0.01). Figure 1: CTDIvol of chest CT exams in male and female patients within different BMI classes. The numbers represent CTDIvol values in mGy. [Fig 1] Figure 2: DLP values of chest CT in male and female patients with different body sizes per...

Conclusions It is possible to generate local DRL for dose optimization purposes. Collection of large datasets of dose information can help generate clinical indication-, BMI- and gender-specific local DRL values which can then be compared with published national or international DRL values for corresponding body regions. Our study points to optimal radiation dose parameters for average size patients (BMI< 25kg/m2) but need for dose optimization in patients with larger body habitus (overweight or obese per WHO classification) based on BMI. Limitations:Data limited to a single...

[1] International Atomic Energy Agency. Bonn Call for Action.[access in 4 jan. 2022]. Available from: https://www.iaea.org/resources/rpop/resources/bonn-call-for-action-platform [2] BSS. International Atomic Energy Agency, Radiation protection and safety of radiation sources: International Basic Safety Standards. IAEA, Vienna [Internet]. IAEA Safety Standards Series No. GSR Part 3; 2014 [access in 4 jan. 2022]. Available from: http://www-pub.iaea.org/books/IAEABooks/8930/Radiation-Protec-tion-and-Safety-of- Radiation-Sources-International-Basic-Safety-Standards. [3] NCRP. Ionizing Radiation Exposure of the Population of the United States. NCRP Report 160, 2009. National Council on Radiation Protection and Measurements, Bethesda, MD. [4] International Commission on Radiation Protection,...

M. O. B. Bernardo: Nothing to disclose F. Morgado: Nothing to disclose S. Ebrahimian: Nothing to disclose A. A. Moscatelli: Nothing to disclose M. C. Cuter Rodel: Nothing to disclose D. M. Sales: Nothing to disclose L. M. Bellegard: Nothing to disclose P. R. P. COSTA: Nothing to disclose M. K. Kalra: Nothing to disclose