Abstract
Objective: To compare image quality and radiation dose of abdominal CT examinations reconstructed with three image reconstruction techniques.
Methods: In this Institutional Review Board-approved study, contrast-enhanced (CE) abdominopelvic CT scans from 23 patients were reconstructed using filtered back projection (FBP), adaptive statistical iterative reconstruction (ASiR) and iterative reconstruction in image space (IRIS) and were reviewed by two blinded readers. Subjective (acceptability, sharpness, noise and artefacts) and objective (noise) measures of image quality were recorded for each image data set. Radiation doses in CT dose index (CTDI) dose-length product were also calculated for each examination type and compared. Imaging parameters were compared using the Wilcoxon signed rank test and a paired t-test.
Results: All 69 CECT examinations were of diagnostic quality and similar for overall acceptability (mean grade for ASiR, 3.9 +/- 0.3; p=0.2 for Readers 1 and 2; IRIS, 3.9 +/- 0.4, p=0.2; FBP, 3.8 +/- 0.9). Objective noise was considerably lower with both iterative techniques (p<0.0001 and 0.0016 for ASiR and IRIS). Recorded mean radiation dose, i.e. CTDIvol, was 24% and 10% less with ASiR (11.4 +/- 3.4 mGy; p<0.001) and IRIS (13.5 +/- 3.7 mGy; p=0.06), respectively, than with FBP: 15.0 +/- 3.5 mGy.
Conclusion: At the system parameters used in this study, abdominal CT scans reconstructed with ASiR and IRIS provide diagnostic images with reduced image noise and 10-24% lower radiation dose than FBP.
Advances in knowledge: CT images reconstructed with FBP are frequently noisy on lowering the radiation dose. Newer iterative reconstruction techniques have different approaches to produce images with less noise; ASiR and IRIS provide diagnostic abdominal CT images with reduced image noise and radiation dose compared with FBP. This has been documented in this study.