The radiation dose from whole body hybrid imaging (PET–CT) procedures in Sri Lanka: The initial approach towards establishing national diagnostic reference level

Abstract

Positron emission tomography-Computed tomography (PET–CT) is a hybrid imaging modality that is increasingly used in the diagnosis and staging of cancer. However, due to its hybrid nature, PET–CT is associated with a high radiation dose, which is a concern for patient safety. The aim of this study is to assess the radiation dose from both components of PET and CT to establish diagnostic reference levels (DRLs) that can be used as a tool for dose optimization. This study presents the results of the initial attempt to establish DRLs for body PET–CT procedures among adults and children in Sri Lanka.Data on the injected activity (MBq) and CT radiation dose, volume CT dose index (CTDIvol) and dose length product (DLP) were collected from three PET–CT centers in Sri Lanka and the institutional diagnostic reference level (IDRL) has been established using the median dose distribution for each center and procedure. The median of the individual IDRLs was presented as the national diagnostic reference level (NDRL). Additionally, the mean, standard deviation, 25th, and 75th percentiles of the pooled dose distribution have been presented with and without weight restrictions for adults, as well as for several age and weight bins for pediatrics.The average injected activity of standard adult patients was 187 ± 37 MBq while for pediatric patients aged 1 to 15 years, it ranged between 105 ± 22 and 139 ± 43 MBq. The average CT dose based on CTDIvol and DLP for a standard adult were 3.81 ± 0.86 mGy and 668 ± 140 mGy.cm. The average CTDIvol and DLP ranged between 2.05 ± 0.76–3.65 ± 1.59 and 195 ± 50–411 ± 188 for pediatric patients. The NDRL based on injected activity for adults and pediatric was 198.3 203.3 MBq and 127.7 MBq. The levels of injected activity for adult patients were found to be lower than those published internationally. However, procedures involving both PET and CT in pediatric patients require dose optimization.The present study proposed IDRL and NDRL values for body PET–CT procedures in Sri Lanka. The findings indicate that these values can serve as an effective guide for achieving further optimization in dose, particularly in procedures involving both PET and CT in pediatric patients.