Purpose
With the increasing value of computed tomography examinations (CT) and its ease of accessibility, we now face a growing concern: radiation exposure and its cumulative effects [1]. In view of this, there is strong advocation for regular quality control and optimization of acquisition protocols in conjunction with the ALARA principle. The objective of this study is to review the radiation dosages and establish facility reference levels (FRLs) for common CT examinations performed in a South Australian tertiary hospital for dose optimisation.
Methods and materials
A retrospective audit of common adult CT examinations performed in January 2020 was conducted. Collected data included patient demographics, anatomic protocol and CT parameters, scanner used (old scanner A and new scanner B), and dose indices (volumetric CT dose index (CTDIvol) and dose-length product (DLP)). The derived median FRLs were compared to current National Diagnostic Reference Levels (NDRLs) recommended by the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) [2,3].
Estimated effective doses (E) were derived from the DLP values using “k” conversion coefficients with...
Results
1800 scans were analysed and categorized based on anatomical regions (table 1): brain (36%), abdomen-pelvis (24%), chest (14%), chest-abdomen-pelvis (12%), cervical spine (6%), kidney-ureter-bladder (4%), soft tissue neck (3%), and lumbar spine (1%).
Several protocols recorded lower median CTDIvol (figure 1) and DLP (figure 2) values compared to the NDRLs, including neck (11mGy; 350mGy.cm), kidney-ureter-bladder (6mGy; 288mGy.cm), chest (9mGy; 361mGy.cm), abdomen-pelvis (8mGy; 420mGy.cm), and chest-abdomen-pelvis (9mGy; 881mGy.cm) .
The median CTDIvol for cervical and lumbar spine were below the NDRL (19mGy and 23mGy respectively) but...
Conclusion
Most of our FRL values are lower or comparable with the NDRLs, with the exception of spine and brain examinations where higher DLP values were obtained. Additionally, significantly variable radiation output between scanners were evident for several protocols, with resulting higher FRL values in brain and chest categories. This suggests the need for protocol review and revision, with emphasis placed on scan length and scanner-specific CT parameters such as tube kilo voltage peak (kVp). Where protocol adjustments are not possible or result in diminished image...
References
Mayo-Smith WW, Hara AK, Mahesh M, Sahani DV, Pavlicek W. How I do it: managing radiation dose in CT. Radiology. 2014 [cited 2021 March 15];273(3):657-672. Available from: https://pubs.rsna.org/doi/pdf/10.1148/radiol.14132328
Australian Radiation Protection and Nuclear Safety Agency. ARPANSA. © Commonwealth of Australia: Australian Radiation Protection and Nuclear Safety Agency [updated 2021 March; cited 2021 March 16]. Available from: https://www.arpansa.gov.au
Lee KL, Beveridge T, Sanagou M, Thomas P. Updated Australian diagnostic reference levels for adult CT.J Med Radiat Sci . 2020 [cited 2021 March 15];67(1):5-15. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7063242/...