First nationwide clinical indication-based diagnostic reference levels incorporating size-specific dose estimates for adult chest CT in Morocco.

PURPOSE: To establish nationwide clinical indication-based multicenter diagnostic reference levels (DRLs) for adult chest CT examinations in Morocco.

METHODS

This retrospective multicenter study included 1,238 adult chest CT examinations grouped into four clinical indications: Lung nodule/follow-up, Infection/ILD/fibrosis, lung cancer staging/lymph node evaluation, and emergency/PE/trauma. For each indication, CTDIvol and dose-length product (DLP) were analyzed. Multicenter DRLs were defined as the 75th percentile of center-level median CTDIvol and DLP values. Differences between indication groups were assessed using the Kruskal-Wallis test, with results reported using medians and 95% confidence intervals.

RESULTS

Dose levels differed significantly between clinical indications for both CTDIvol and DLP (p < 0.001). Emergency/PE/trauma examinations showed the highest patient-level dose values, followed by lung cancer staging/lymph node evaluation, infection/ILD/fibrosis, and lung nodule/follow-up. Patient-level P75 values for CTDIvol were 10.11, 7.10, 5.00, and 4.80 mGy, respectively, while corresponding DLP P75 values were 439.78, 339.60, 250.00, and 214.60 mGy·cm.

CONCLUSION

Adult chest CT dose levels vary substantially according to clinical indication. Clinical indication-based multicenter DRLs provide a more appropriate optimization framework than a single anatomy-based chest CT DRL and should be used to guide protocol harmonization and dose optimization in Moroccan CT practice.