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Effect of reconstruction methods and x-ray tube current-time product on nodule detection in an anthropomorphic thorax phantom : a crossed-modality JAFROC observer study

Thompson, John D., Chakraborty, DP, Szczepura, Katy, Tootell, AK, Vamvakas, I, Manning, DJ and Hogg, P 2016, 'Effect of reconstruction methods and x-ray tube current-time product on nodule detection in an anthropomorphic thorax phantom : a crossed-modality JAFROC observer study' , Medical Physics, 43 (1265) .

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Abstract

Purpose: To evaluate nodule detection in an anthropomorphic chest phantom in computed tomography (CT) images reconstructed with adaptive iterative dose reduction 3D (AIDR3D) and filtered back projection (FBP) over a range of tube current-time product (mAs). Methods: Two phantoms were used in this study: (i) an anthropomorphic chest phantom was loaded with spherical simulated nodules of 5, 8, 10 and 12mm in diameter and +100, -630 and -800 Hounsfied Units electron density; this would generate CT images for the observer study; (ii) a whole-body dosimetry verification phantom was used to ultimately estimate effective dose and risk according to the model of the BEIR VII committee. Both phantoms were scanned over a mAs range (10, 20, 30, and 40) while all other acquisition parameters remained constant. Images were reconstructed with both AIDR3D and FBP. 34 normal cases (no nodules) and 34 abnormal cases (containing 1-3 nodules, mean 1.35±0.54) cases were chosen for the observer study. Eleven observers evaluated images from all tube current-time product and reconstruction methods under the free-response paradigm. A crossed-modality jackknife alternative free-response operating characteristic (JAFROC) analysis method was developed for data analysis, averaging data over the two factors influencing nodule detection in this study: mAs and image reconstruction (AIDR3D or FBP). A Bonferroni correction was applied and the threshold for declaring significance was set at 0.025 to maintain the overall probability of Type I error at α = 0.05. Contrast-to-noise (CNR) was also measured for all nodules and evaluated by a linear least squares analysis. Results: For random-reader fixed-case crossed-modality JAFROC analysis there was no significant difference in nodule detection between AIDR3D and FBP when data was averaged over mAs (F(1,10) = 0.08, p = 0.789). However, when data was averaged over reconstruction methods, a significant difference was seen between multiple pairs of mAs settings (F(3,30) = 15.96, p<0.001). Measurements of effective dose and effective risk showed the expected linear dependence on mAs. Nodule CNR was statistically higher for simulated nodules on images reconstructed with AIDR3D (p<0.001). Conclusion: No significant difference in nodule detection performance was demonstrated between images reconstructed with FBP and AIDR3D. Tube current-time product was found to influence nodule detection, though further work is required for dose optimisation.

Item Type: Article
Schools: Schools > School of Health Sciences > Centre for Health Sciences Research
Journal or Publication Title: Medical Physics
Publisher: American Association of Physicists in Medicine:
ISSN: 0094-2405
Related URLs:
Funders: Non funded research
Depositing User: WM Taylor
Date Deposited: 16 Feb 2016 11:30
Last Modified: 18 Apr 2016 07:49
URI: http://usir.salford.ac.uk/id/eprint/37975

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