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Comparative Study
. 2013 Jan;86(1021):20120161.
doi: 10.1259/bjr.20120161.

Comparative Assessment of Three Image Reconstruction Techniques for Image Quality and Radiation Dose in Patients Undergoing Abdominopelvic Multidetector CT Examinations

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Free PMC article
Comparative Study

Comparative Assessment of Three Image Reconstruction Techniques for Image Quality and Radiation Dose in Patients Undergoing Abdominopelvic Multidetector CT Examinations

G S Desai et al. Br J Radiol. .
Free PMC article

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. CTDI(vol), 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.

Figures

Figure 1
Figure 1
Flowchart depicting the study design. ASiR, adaptive statistical iterative reconstruction; CE, contrast enhanced; FBP, filtered back projection; IRIS, iterative reconstruction in image space; NC, non-contrast enhanced.
Figure 2
Figure 2
Coronal CT images reconstructed using filtered back projection (FBP), adaptive statistical iterative reconstruction (ASiR) and iterative reconstruction in image space (IRIS) in a 58-year-old female weighing 59.7 kg (131.8 lb) with liver metastases (arrow), pancreatic calcification (arrows) and splenomegaly (*) shown. The FBP (a) examination was performed with an effective radiation dose of 10 mSv [volume CT dose index (CTDIvol), 15.7 mGy; dose–length product (DLP), 665 mGy cm] while the subsequent examinations reconstructed using ASiR (b) and IRIS (c) were performed at a reduced radiation dose of 36.9% [CTDIvol, 9.9 mGy; DLP, 552.3 mGy cm; effective dose (ED), 8.3 mSv] and 14.1% (CTDIvol, 13.5 mGy; DLP, 652 mGy cm; ED, 10.1 mSv), respectively. The image quality and objective image noise were comparable in the three examinations.
Figure 3
Figure 3
A 57-year-old female weighing 69.8 kg (153.8 lb) with a history of endometrial carcinoma underwent serial examinations as part of her disease workup. Axial filtered back projection (FBP) image (a) shows multiple haemangiomas in the liver. Axial images from the follow up restaging examinations reconstructed using adaptive statistical iterative reconstruction (ASiR) (b) and iterative reconstruction in image space (IRIS) (c) were of diagnostic quality despite using a 28–33% lower dose than FBP examinations (ASiR: 448.9 mGy.cm, IRIS: 483 mGy.cm vs FBP: 670.5 mGy.cm).

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