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Proceedings Paper

A phantom-based JAFROC observer study of two CT reconstruction methods: the search for optimisation of lesion detection and effective dose
Author(s): John D. Thompson; Dev P. Chakraborty; Katy Szczepura; Ioannis Vamvakas; Andrew Tootell; David J. Manning; Peter Hogg
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Paper Abstract

Purpose: To investigate the dose saving potential of iterative reconstruction (IR) in a computed tomography (CT) examination of the thorax.

Materials and Methods: An anthropomorphic chest phantom containing various configurations of simulated lesions (5, 8, 10 and 12mm; +100, -630 and -800 Hounsfield Units, HU) was imaged on a modern CT system over a tube current range (20, 40, 60 and 80mA). Images were reconstructed with (IR) and filtered back projection (FBP). An ATOM 701D (CIRS, Norfolk, VA) dosimetry phantom was used to measure organ dose. Effective dose was calculated. Eleven observers (15.11±8.75 years of experience) completed a free response study, localizing lesions in 544 single CT image slices. A modified jackknife alternative free-response receiver operating characteristic (JAFROC) analysis was completed to look for a significant effect of two factors: reconstruction method and tube current. Alpha was set at 0.05 to control the Type I error in this study.

Results: For modified JAFROC analysis of reconstruction method there was no statistically significant difference in lesion detection performance between FBP and IR when figures-of-merit were averaged over tube current (F(1,10)=0.08, p = 0.789). For tube current analysis, significant differences were revealed between multiple pairs of tube current settings (F(3,10) = 16.96, p<0.001) when averaged over image reconstruction method.

Conclusion: The free-response study suggests that lesion detection can be optimized at 40mA in this phantom model, a measured effective dose of 0.97mSv. In high-contrast regions the diagnostic value of IR, compared to FBP, is less clear.

Paper Details

Date Published: 17 March 2015
PDF: 6 pages
Proc. SPIE 9416, Medical Imaging 2015: Image Perception, Observer Performance, and Technology Assessment, 94160B (17 March 2015); doi: 10.1117/12.2081632
Show Author Affiliations
John D. Thompson, Univ. of Salford (United Kingdom)
Univ. Hospitals of Morecambe Bay NHS Foundation Trust (United Kingdom)
Dev P. Chakraborty, Univ. of Pittsburgh (United States)
Katy Szczepura, Univ. of Salford (United Kingdom)
Ioannis Vamvakas, The Christie NHS Foundation Trust (United Kingdom)
Andrew Tootell, Univ. of Salford (United Kingdom)
David J. Manning, Lancaster Univ. (United Kingdom)
Peter Hogg, Univ. of Salford (United Kingdom)

Published in SPIE Proceedings Vol. 9416:
Medical Imaging 2015: Image Perception, Observer Performance, and Technology Assessment
Claudia R. Mello-Thoms; Matthew A. Kupinski, Editor(s)

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