Abstract
ObjectiveTo step-wise evaluate image quality of sinogram-affirmed iterative reconstruction (SAFIRE) in reduced-dose (RD) thoracoabdominal computed tomography (CT) compared to full-dose (FD) and RD filtered back projection (FBP) in a longitudinal study.Materials and methods122 patients were included in this prospective study. 49 patients (14 men: mean age ± SD, 56±0.4 years; 35 women: 58±1.3 years) completed FD, RD1 (80%-dose) and RD2 (60%-dose) thoracoabdominal CT. Each CT dataset was reconstructed with FBP and SAFIRE. For quantitative image analysis image noise was measured in defined tissue regions. Qualitative image evaluation was performed according to the European Guidelines on Quality criteria for CT. Additionally artifacts, lesion conspicuity, and edge sharpness were assessed.ResultsCompared to FD-FBP noise in soft tissue increased by 12% in RD1-FBP and 27% in RD2-FBP reconstructions, whereas SAFIRE lead to a decrease of 28% (RD1) and 17% (RD2), respectively (all p <0.001). Visually sharp reproduction, lesion conspicuity, edge sharpness of pathologic findings, and overall image quality did not differ statistically significant between FD-FBP and RD-SAFIRE datasets. Image quality decreased in RD1- and RD2-FBP compared to FD-FBP, reaching statistically significance in RD2 datasets (p <0.001). In RD1- and RD2-FBP (p <0.001) streak artifacts were noted.ConclusionUsing SAFIRE the reference mAs in thoracoabdominal CT can be reduced by at least 30% in clinical routine without loss of image quality or diagnostic information.
Highlights
The increase in radiation exposure from diagnostic testing is of growing concern
Compared to FD-filtered back projection (FBP) noise in soft tissue increased by 12% in RD1-FBP and 27% in RD2FBP reconstructions, whereas sinogram-affirmed iterative reconstruction (SAFIRE) lead to a decrease of 28% (RD1) and 17% (RD2), respectively
Lesion conspicuity, edge sharpness of pathologic findings, and overall image quality did not differ statistically significant between FD-FBP and RD-SAFIRE datasets
Summary
The increase in radiation exposure from diagnostic testing is of growing concern. From 1980 to 2010 the annual per capita diagnostic radiation dose in the United States increased four to five times from 0.5 mSv to 2.3 mSv [1, 2]. Decreasing radiation exposure is associated with an increase in image noise and at a certain level results in unacceptable loss of diagnostic performance [7]. To overcome these limitations and improve image quality in reduced-dose (RD) CT, iterative reconstruction techniques, as a rather old method for image optimization [8], are increasingly applied in clinical routine. Sinogram-affirmed iterative reconstruction (SAFIRE, Siemens Healthcare, Forchheim, Germany) is an algorithm applied on Siemens CT systems without Stellar detectors It has been demonstrated in previous studies, that the higher image noise of RD abdominal CT can be minimized with iterative reconstruction algorithms, enabling substantial radiation dose savings with preserved diagnostic image quality [10, 11]. Three consecutive thoracoabdominal CT scans with a step-wise dose reduction from 100% to 80% and 60% were performed
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