Aortic Valve and Thoracic Aortic Calcification Measurements: How Low Can We Go in Radiation Dose?

Objective: This study aimed to determine the lowest radiation dose and iterative reconstruction level(s) at which computed tomography (CT)' based quantification of aortic valve calcification (AVC) and thoracic aortic calcification (TAC) is still feasible. Methods: Twenty-eight patients underwent a cardiac CTand 20 patients a chest CTat ⁴ different dose levels (routine dose and approximately 40%, 60%, and 80% reduced dose). Data were reconstructed with filtered back projection, 3 iDose4 levels, and 3 iterative model-based reconstruction levels. Two observers scored subjective image quality. The AVC and TAC were quantified usingmassandcomparedtothe reference scan(routine dosereconstructedwith filtered back projection). Results: In cardiac CT at 0.35 mSv (60% reduced), all scans reconstructed with iDose4 (all levels) were diagnostic, calcification detection errors occurred in only 1 patient, and there were no significant differences in mass scores compared to the reference scan. Similar results were found for chest CT at 0.48 mSv (75% reduced) with iDose4 levels 4 and 6 and iterative model reconstruction levels 1 and 2. Conclusions: Iterative reconstruction enables AVC and TAC quantification on CT at submillisievert dose.