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

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.