Purpose To evaluate the image quality of an iterative reconstruction algorithm (IRIS) in low-dose chest CT in comparison with standard-dose filtered back projection (FBP) CT. Materials and methods Eighty consecutive patients referred for a follow-up chest CT examination of the chest, underwent a low-dose CT examination (Group 2) in similar technical conditions to those of the initial examination, (Group 1) except for the milliamperage selection and the replacement of regular FBP reconstruction by iterative reconstructions using three (Group 2a) and five iterations (Group 2b). Results Despite a mean decrease of 35.5% in the doselength-product, there was no statistically significant difference between Group 2a and Group 1 in the objective noise, signal-to-noise (SNR) and contrast-to-noise (CNR) ratios and distribution of the overall image quality scores. Compared to Group 1, objective image noise in Group 2b was significantly reduced with increased SNR and CNR and a trend towards improved image quality. Conclusion Iterative reconstructions using three iterations provide similar image quality compared with the conventionally used FBP reconstruction at 35% less dose, thus enabling dose reduction without loss of diagnostic information. According to our preliminary results, even higher dose reductions than 35% may be feasible by using more than three iterations.

Objective To assess noise reduction achievable with an iterative reconstruction algorithm. Methods 32 consecutive chest CT angiograms were reconstructed with regular filtered back projection (FBP) (Group 1) and an iterative reconstruction technique (IRIS) with 3 (Group 2a) and 5 (Group 2b) iterations.

http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12120414/-/DC1.

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• Iterative reconstruction does not alter the detection of endoluminal clots. • Iterative reconstruction allows dose reduction in the context of acute PE. • Iterative reconstruction allows radiologists to approach the prospects of submilliSievert CT.

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Background and objective: Real-time compressed sensing cine (CSrt) provides reliable quantification for both ventricles but may alter image quality. The aim of this study was to assess image quality and the accuracy of left (LV) and right ventricular (RV) volumes, ejection fraction and mass quantifications based on a retrogated segmented compressed sensing 2D cine sequence (CSrg). Methods: Thirty patients were enrolled. Each patient underwent the reference retrogated segmented steady-state free precession cine sequence (SSFPref), the real-time CSrt cine and the segmented retrogated prototype CSrg sequence providing the same slices. Functional parameters quantification and image quality rating were performed on SSFPref and CSrg images sets. The edge sharpness, which is an estimate of the edge spread function, was assessed for the three sequences. Results: The mean scan time was: SSFPref = 485.4 ± 83.3 (SD) s (95% CI: 454.3–516.5) and CSrg = 58.3 ± 15.1 (SD) s (95% CI: 53.7–64.2) (p < 0.0001). CSrg subjective image quality score (median: 4; range: 2–4) was higher than the one provided by CSrt (median: 3; range: 2–4; p = 0.0008) and not different from SSFPref overall quality score (median: 4; range: 2–4; p = 0.31). CSrg provided similar LV and RV functional parameters to those assessed with SSFPref (p > 0.05). Edge sharpness was significantly better with CSrg (0.083 ± 0.013 (SD) pixel−1; 95% CI: 0.078–0.087) than with CSrt (0.070 ± 0.011 (SD) pixel−1; 95% CI: 0.066–0.074; p = 0.0004) and not different from the reference technique (0.075 ± 0.016 (SD) pixel−1; 95% CI: 0.069–0.081; p = 0.0516). Conclusions: CSrg cine provides in one minute an accurate quantification of LV and RV functional parameters without compromising subjective and objective image quality.

Higher temporal resolution improved the visibility of proximal coronary arteries in pediatric chest CT.