Phantom study of the impact of adaptive statistical iterative reconstruction (ASiR^TM) on image quality for paediatric computed tomography

Angjelina Protik, Karen Thomas, Paul Babyn, Nancy L. Ford

Department of Medical Imaging, University of Saskatchewan, Saskatoon, Canada.
Department of Medical Imaging, University of Toronto, Toronto, Canada.
Department of Oral Biological and Medical Sciences, University of British Columbia, Vancouver, Canada.
Department of Physics, Ryerson University, Toronto, Canada.

DOI: 10.4236/jbise.2012.512A100                

Abstract

Quantitative analysis of image quality will be helpful for designing ASiR^TM-enhanced paediatric CT protocols, balancing image quality and radiation dose. Catphan600 phantom studies were performed on a GE Discovery HD750 64-slice CT scanner. Images were reconstructed with 0% - 100% ASiR^TM (tube current 150 mA, variable kVp 80 - 140) in order to determine the optimal ASiR^TM-Filtered Back Projection (FBP) blend. Images reconstructed with a 50% ASiR^TM-50% FBP blend were compared to FBP images (0% ASiR^TM) over a wide range of kVp (80 - 140) and mA (10 - 400) values. Measurements of image noise, CT number accuracy and uniformity, spatial and contrast resolution, and low contrast detectability were performed on axial and reformatted coronal images. Improvements in CNR, low contrast detectability and radial uniformity were observed in ASiR^TM images compared to FBP images. 50% ASiR^TM was associated with a 26% - 30% reduction in image noise. Changes in noise texture were observed at higher % ASiR^TM blends with impact on visualisation of low and high contrast objects. A small decrease in limiting spatial resolution was detected with addition of ASiR^TM, more appreciable at very low tube currents. The preferred blend for paediatric body protocols in our study, as determined by the image quality parameters investigated, was 50% ASiR^TM when used with tube currents greater than 50 mA.

Keywords

Image Analysis; CT; Optimization; ASiR^TM; Paediatric Imaging

Conflicts of Interest

The authors declare no conflicts of interest.

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