Australian medical imaging providers are required under the ARPANSA Code of Practice (RPS C-5 Section 3.2.15, previously RPS 14 Section 3.1.8) to regularly compare typical patient doses to the national diagnostic reference levels (DRLs).
ARPANSA's NDRLS provides free tools for conducting dose comparisons: login or register for the multi-detector CT survey here or see the relevant imaging modality section for details.