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Image Comparative Assessment Using Iterative Reconstructions: Clinical Comparison of Low-Dose Abdominal/Pelvic Computed Tomography Between Adaptive Statistical, Model-Based Iterative Reconstructions and Traditional Filtered Back Projection in 65 Patients

Vardhanabhuti, Varut MBBS, FRCR*†; Riordan, Richard D. MRCP, FRCR*; Mitchell, Grant R. MRCP, FRCR*†; Hyde, Christopher MRCP, FFPH; Roobottom, Carl A. MRCP, FRCR*†

doi: 10.1097/RLI.0000000000000017
Original Articles

Objectives: The objective of this study was to compare image quality (objective and subjective parameters) and confidence in lesion detection between 3 image reconstruction algorithms in computed tomographic (CT) examinations of the abdomen/pelvis.

Materials and Methods: This prospective institutional review board–approved study included 65 patients (mean [SD] age, 71.3 ± 9 years; mean [SD] body mass index, 24.4 [4.8] kg) who underwent routine CT examinations of the abdomen/pelvis followed immediately by 2 low-dose scans. Raw data sets were reconstructed by using filtered back projection (FBP), adaptive statistical iterative reconstruction (ASIR), and a model-based iterative reconstruction (MBIR). Measurements of objective noise and CT numbers were compared using repeated-measures analysis of variance. Six subjective image quality parameters were scored. Diagnostic confidence and accuracy in detection of various elementary lesions were performed.

Results: Objectively, mean image noise for MBIR was significantly superior at all dose levels (P < 0.001). Subjectively, standard-dose ASIR and low-dose MBIR scans were better than standard-dose FBP scan in all parameters assessed (P < 0.05). Low-dose MBIR scans were comparable with standard-dose ASIR scans in all parameters except at noise index of 70 (approximately 85% dose reduction), where, in this case, the detection of liver lesions less than 5 mm were rated inferior (P < 0.05) with diagnostic accuracy reducing to 77.4%.

Conclusions: Low-dose MBIR scan shows superior objective noise reduction compared with standard-dose FBP and ASIR. Subjectively, low-dose MBIR scans at 76% dose reduction were also superior compared with standard-dose FBP and ASIR. However, at dose reductions of 85%, small liver lesions may be missed.

From the *Department of Radiology, Derriford Hospital; †Plymouth University Peninsula Schools of Medicine and Dentistry, Plymouth; and ‡University of Exeter Medical School, Exeter, United Kingdom.

Received for publication May 5, 2013; and accepted for publication, after revision, October 23, 2013.

Conflicts of interest and sources of funding: none declared.

Reprints: Varut Vardhanabhuti, MBBS, FRCR, Department of Radiology, Derriford Hospital, Derriford Rd, Plymouth, Devon, PL6 8DH, United Kingdom. E-mail:

© 2014 by Lippincott Williams & Wilkins