A survey of diagnostic reference levels for head, chest, and abdomen and pelvis CT in private diagnostic facilities in Norway

Background:
Computed tomography (CT) scans account for 60% of the total radiation dose in medical imaging. Literature has shown that patient dose varies across CT scanners, diagnostic protocols, and technical parameters at each site, suggesting an opportunity for starting an optimization process through establishing diagnostic reference levels (DRLs).

Purpose:
To establish local DRLs (LDRLs) for six Norwegian private diagnostic institutes for frequently performed CT protocols.

Material and Methods:
Dose data from 900 patients were collected from six diagnostic facilities. Data were recorded from non-contrast CT scans of the head and contrast-enhanced scans of the thorax and abdomen and pelvis from average-sized adult patients. An ANOVA test was performed to determine the variation in dose between scanners. LDRLs were determined by the 75th percentile of median values from dose indicators of CT scanners.

Results:
The difference between the means of the dose distribution from each scanner was statistically significant (P < 0,05) for all examinations. The LDRLs determined were lower, for both national and international DRLs.

Conclusion:
Observed dose variations from the scanners indicate a need for protocol optimization for some institutes, while the LDRLs demonstrate a potential for establishing newer national diagnostic reference levels (NDRLs) in Norway.