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Does Resampled Image Data Offer Quantitative Image Quality Benefit for Pediatric CT?

Journal of Biomedical Science and Engineering 2014年第6期7卷 343-350页

作者： Nancy L. Ford angjelina protik Paul Babyn Karen Thomas Ryerson University Toronto Canada The Hospital for Sick Children and University of Toronto Toronto Canada University of British Columbia Vancouver Canada University of Saskatchewan Saskatoon Canada

Acquiring CT images with thin slices can improve resolution and detectability, but cause an increase in the image noise. To compensate for the additional image noise, the kVp or mA can be increased, which carries a dose penalty to the patient. We investigate the image quality achieved in MPR images reformatted from different slice thicknesses 0.625 mm and 5 mm, to determine if a thicker slice could be resampled to smaller thickness with minimal loss of image information. Catphan?600 phantom was imaged using selected kVp/mA settings (80 kVp/250 mA, 100 kVp/ 150 mA and 120 kVp/200 mA) to generate slices with thicknesses of 0.625 mm and 5 mm using a GE Discovery HD750 64-slice CT scanner to investigate the impact of the acquisition slice thickness on the overall image quality in MPRs. Measurements of image noise, uniformity, contrast-to-noise ratio (CNR), low contrast detectability and limiting spatial resolution were performed on axial and coronal multiplanar reformatted images (MPRs). Increased noise, reduced contrast-to-noise ratio, and improved limiting spatial resolution and low contrast detection were observed in 2 mm coronal MPRs generated with 0.625 mm thin slices when compared to the MPRs from 5 mm thick slices. If the 2 mm coronal MPRs acquired with 5 mm slices are resampled to 0.6 mm slice thickness, the reductions in limiting resolution and low contrast detection are compensated, although with reduced uniformity and increased image noise. Thick slice image acquisitions yield better CNR and less noise in the images, whereas thin slices exhibited improved spatial resolution and low contrast detectability. Retrospectively resampling into thinner slices before obtaining the coronal MPRs provided a balance between image smoothness and identifying fine image detail. Which approach provides the optimal image quality may also depend on the imaging task, size and composition of the features of interest, and radiologist preference.

关键词： Paediatric CT Image Quality Multiplanar Reformats (MPR) Collimation

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

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Journal of Biomedical Science and Engineering 2012年第12期5卷 793-806页

作者： 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

Quantitative analysis of image quality will be helpful for designing ASiRTM-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% ASiRTM (tube current 150 mA, variable kVp 80 - 140) in order to determine the optimal ASiRTM-Filtered Back Projection (FBP) blend. Images reconstructed with a 50% ASiRTM-50% FBP blend were compared to FBP images (0% ASiRTM) 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 ASiRTM images compared to FBP images. 50% ASiRTM was associated with a 26% - 30% reduction in image noise. Changes in noise texture were observed at higher % ASiRTM blends with impact on visualisation of low and high contrast objects. A small decrease in limiting spatial resolution was detected with addition of ASiRTM, 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% ASiRTM when used with tube currents greater than 50 mA.

关键词： Image Analysis CT Optimization ASiRTM Paediatric Imaging

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