Low-dose, wide-detector array thoracic aortic CT angiography using an iterative reconstruction technique results in improved image quality with lower noise and fewer artifacts.

BACKGROUND: Iterative reconstruction techniques (IRTs) may improve image quality for low-dose imaging compared with filtered back projection (FBP) reconstruction.

OBJECTIVES: We compared the results of an IRT for low-dose thoracic aortic computed tomography (CT) imaging with those from FBP reconstruction.

METHODS: Data from 50 patients who underwent 256-slice CT for evaluation of the thoracic aorta were reconstructed with FBP and an IRT (iDose(4)) at 3 noise-reduction strengths (levels 2, 4, and 6). A blinded reader graded image quality (scale, 1-5; 5 = high diagnostic confidence) and the extent of shoulder artifact (scale, 1-5; 5 = no artifact) on all reconstructions. A second reader evaluated a subset of 20 cases to determine interreader and intrareader reproducibility. The mean and SD of attenuation were measured at 5 locations along the thoracic aorta and both subclavian arteries.

RESULTS: Image noise (SD of attenuation) improved with IRT relative to FBP (aorta: FBP, 31.4 ± 8.6 HU; IRT level 2, 25.1 ± 6.9 HU; level 4, 21.7 ± 6.2 HU; level 6, 17.2 ± 5.4 HU; P < 0.0001; subclavian arteries: FBP, 92.7 ± 34.6 HU; IRT level 2, 50.1 ± 17.1 HU; level 4, 48.9 ± 18.6 HU; level 6, 45.2 ± 19.2 HU; P < 0.0001), whereas mean attenuation was unchanged. Increasing image quality was observed in the aorta and through the shoulders as the contribution from IRT to the final images increased (P < 0.0001). Significant differences were noted between readers in image quality assessment of the aorta but not through the shoulders.

CONCLUSION: IRT is associated with reduced noise and shoulder artifact and allows for low-dose aortic CT imaging.