Keywords:
Radiation physics, Radioprotection / Radiation dose, CT, Dosimetry, Physics, Radiation safety, Dosimetric comparison
Authors:
I. Kralik, B. Brkljacic, D. Cvetko, I. Hulina, M. Justić, J. Popić, I. Bjelobrk, T. Turk, D. Faj
Results or findings
The results of the analysis show that for the same clinical indication, imaging is performed differently in different hospitals and in some cases differently when more CT units are used at the same hospital, starting with the use of different numbers of phases (precontrast and postcontrast) (Figure 1).
In some cases where examination is performed using different number of phases for the same indication using the same CT unit, data for insufficient number of patients was provided for specific phase hence for that phase typical values were not calculated (such phases are marked in red in Figure 1).
Variation in practice is also visible when calculated typical values for CTDIvol, DLP and L for each phase and for total DLP are compared with EU DRL values as given in RP 195 and with nDRLs (Figures 2-5).
Only in case of the following indications and CT units typical values for CTDIvol, DLP and L for each phase and for the total DLP are lower than RP 195 EU DRL values:
- Indication 2 (Stroke - Detection or exclusion of a haemorrhage): CT 4 (H2)
- Indication 4 (Pulmonary embolism - Detection or exclusion): CT4 (H2) and CT6 (H3)
- Indication 7 (Lung cancer - Oncological staging, First and F-up): CT6 (H3)
In all other cases, typical value for at least one of the parameters is greater than RP 195 EU DRL value.
It is interesting to note that the typical value of some dose indices in some cases is below the nDRL, but it is significantly above the EU DRL given in RP 195 (for example, indication 9 & CT 4(H2) for total DLP), which further emphasizes the need to introduce and use clinical DRLs instead of those based on anatomical region.