Slice NEQ and system DQE to assess CT imaging performance.

Details

Serval ID
serval:BIB_8E65A6F7335A
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
Slice NEQ and system DQE to assess CT imaging performance.
Journal
Physics in medicine and biology
Author(s)
Monnin P., Viry A., Verdun F.R., Racine D.
ISSN
1361-6560 (Electronic)
ISSN-L
0031-9155
Publication state
Published
Issued date
09/06/2020
Peer-reviewed
Oui
Volume
65
Number
10
Pages
105009
Language
english
Notes
Publication types: Journal Article
Publication Status: epublish
Abstract
The standard Fourier metrics used for assessing image quality in computed tomography (CT) use a planar (2D) formulation of the noise equivalent quanta (NEQ) without a specific concept to manage the influence of longitudinal resolution variations, thus create a bias in the comparison of image quality for different reconstructed slice thicknesses. For this work, we designed a 'slice NEQ' that takes the longitudinal resolution into account and provides a volumetric indication of the scanner imaging performance. We also developed a specific formulation for the system DQE at the CT isocentre. A cylindrical water phantom with three different inserts for three contrast levels (-100, 120 and 1000 HU) was used for the task-based transfer functions (TTF) and noise power spectra (NPS) measurements. The longitudinal TTF was measured using the point source of the Catphan <sup>®</sup> 600 phantom. Images of the phantoms were acquired on two scanners (GE Discovery 750 HD and Siemens SOMATOM Force) and reconstructed using different slice thicknesses between 1 and 5 mm and algorithms (FBP for both systems, ASIR 50 and ASIR-V 50 for the GE). The slice NEQ correctly compared the imaging performance for different longitudinal resolutions whereas the 2D NEQ increased proportionally with the reconstructed slice thickness. The system DQE peaked at 0.70 (at 0.1 mm <sup>-1</sup> ) for the Siemens and at 0.50 (at 0.1 mm <sup>-1</sup> ) for the GE for FBP reconstructions. The validity of these Fourier-based metrics was restricted to a limited range of contrast due to nonlinearities introduced when dealing with iterative reconstructions (IR).
Keywords
computed tomography, detective quantum efficiency, image quality, noise equivalent quanta, quality controls
Pubmed
Web of science
Open Access
Yes
Create date
02/04/2020 16:54
Last modification date
02/03/2021 7:26
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