National reference levels of CT procedures dedicated for treatment planning in radiation oncology

Published:March 14, 2022DOI:


      • DRLs can help the imaging related to treatment planning in radiation oncology.
      • The intention is to propose RPRLs and compare these values with published data.
      • Results show variations in CT planning which call for optimization of procedures.



      To present results of the first national survey on reference levels of CT imaging performed for the treatment planning purposes in radiation oncology in Croatia.


      Data for CT protocols of five anatomical regions including head, head and neck, pelvis, breast, and thorax were collected at eight radiation oncology departments in Croatia. Data included volume CT dose index (CTDIvol), dose-length product (DLP), scan length and set of acquisition and reconstruction parameters. Data on a total of 600 patients were collected. Median values of scan length, DLP and CTDIvol were calculated for each acquisition protocol. Third quartiles of the median CTDIvol and DLP values were proposed as the national radiotherapy planning reference levels (RPRL).


      The largest CoV were assessed for RT Breast (63.8% for CTDIvol), RT Thorax (79.7% for DLP) and RT H&N (21.2% for scan length). RT Head had the lowest CoV for CTDIvol (1,9%) and DLP (17,2%), while RT Breast had the lowest coefficient of variation for scan length (12.8%). Proposed national RPRLs are: for RT Head CTDIvol16cm = 62 mGy and DLP16cm = 1738; for RT H&N CTDIvol16cm = 35 mGy and DLP16cm = 1444; for RT Breast CTDIvol32cm = 16 mGy and DLP32cm = 731; for RT Thorax CTDIvol32cm = 17 mGy and DLP32cm = 865; for RT Pelvis CTDIvol32cm = 20 mGy and DLP32cm = 1133


      Results of this study show variations in CT imaging for treatment planning practice at the national level which call for optimization of procedures.


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