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Virtual non-contrast dual-energy CT compared to single-energy CT of the urinary tract: a prospective study
Department of Radiology, Örebro University Hospital, 701 85 Örebro, Sweden.
Department of Radiology, Örebro University Hospital, 701 85 Örebro, Sweden.
Department of Radiology, Örebro University Hospital, 701 85 Örebro, Sweden.
Department of Radiology, Örebro University Hospital, 701 85 Örebro, Sweden.
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2012 (English)In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 53, no 6, 689-694 p.Article in journal (Refereed) Published
Abstract [en]

Background: Dual-energy computed tomography (DECT) has been shown to be useful for subtracting bone or calcium in CT angiography and gives an opportunity to produce a virtual non-contrast-enhanced (VNC) image from a series where contrast agents have been given intravenously. High noise levels and low resolution have previously limited the diagnostic value of the VNC images created with the first generation of DECT. With the recent introduction of a second generation of DECT, there is a possibility of obtaining VNC images with better image quality at hopefully lower radiation dose compared to the previous generation.

Purpose: The aim of this study is to compare the image quality of the single-energy series to a VNC series obtained with a two generations of DECT scanners. CT of the urinary tract was used as a model.

Material and Methods: Thirty patients referred for evaluation of haematuria were examined with an older system (Somatom Definition) and another 30 patients with a new generation (Somatom Definition Flash). One single-energy series was obtained before and one dual-energy series after administration of intravenous contrast media. We created a VNC series from the contrast-enhanced images. Images were assessed concerning image quality with a visual grading scale evaluation of the VNC series with the single-energy series as gold standard.

Results: The image quality of the VNC images was rated inferior to the single-energy variant for both scanners, OR range 11.5-67.3 for the Definition and OR 2.1-2.8 for the Definition Flash. Visual noise and overall quality were regarded as better with Flash than Definition.

Conclusions: Image quality of VNC images obtained with the new generation of DECT is still slightly inferior compared to native images. However the difference is smaller with the new compared to the older system.

Place, publisher, year, edition, pages
Informa Healthcare, 2012. Vol. 53, no 6, 689-694 p.
Keyword [en]
Dual-energy computed tomography, image quality, urinary tract imaging, virtual non-enhanced image series, bone-iodine differentiation
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-76721DOI: 10.1258/ar.2012.110661ISI: 000306984000017OAI: oai:DiVA.org:liu-76721DiVA: diva2:516376
Available from: 2012-04-18 Created: 2012-04-18 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Aspects on Image Quality in Radiologic Evaluation of the Urinary Tract
Open this publication in new window or tab >>Aspects on Image Quality in Radiologic Evaluation of the Urinary Tract
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The focus of this document is on image quality as one of the factors fundamental for the diagnostic process. With the rising number of procedures and the trend towards more complicated examinations, urinary tract investigations was chosen in this work as a good clinical model for evaluation of the factors influencing image quality and of the ways of evaluating image quality.

In paper I, a method is described for optimisation during the introduction of a new imaging system, with a focus on the maintenance of image quality relative to the older already optimised system. Image quality was assessed using the image criteria of the European guidelines for IVU with visual grading analysis. Equivalent image quality in image pairs was achieved at 30% of the dose. The CDRAD contrast-detail phantom makes it possible to find dose levels that give equal image quality using different imaging systems.

In paper II, the influence of bowel purgation on image quality in urography is questioned. The aim of this study was to compare bowel purgation and two other preparation methods; dietary restrictions and no preparation at all. Image quality was assessed according to European Commission criteria for excretory urography. The effectiveness of bowel purgation and the amount of residual gas were scored separately. The results of our study show that the preparation methods are of equal value and further use of bowel purgation before excretory urography cannot be justified.

In paper III, the image quality of the non-enhanced series is compared to a virtual noncontrast series obtained using two generations of dual-energy CT scanners and taking CT of the urinary tract as a model. The image quality of the VNC images was rated inferior to the single-energy variant for both scanners, the OR range being 11.5–67.3 for the Definition and 2.1–2.8 for the Definition Flash. Visual noise and overall quality were regarded as better with Flash than with Definition. Image quality of VNC images obtained with the new generation of DECT is still slightly inferior compared to native images.

In paper IV, the accuracy of measurement of renal calculi in a dual-energy, virtual, nonenhanced-image series is compared to actual stone size and a single-energy image series in the phantom study. This study shows that detection of small stones is not reliable, despite better image quality, with the new DECT and that small stones will be missed with VNC imaging. With larger stones, the inherent measurement error with CT is magnified with VNC imaging.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2012. 69 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1298
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:liu:diva-76723 (URN)978-91-7519-943-6 (ISBN)
Public defence
2012-05-18, Bohmansonssalen, Universitetssjukhuset, Örebro, 09:00 (Swedish)
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Available from: 2012-04-18 Created: 2012-04-18 Last updated: 2013-10-21Bibliographically approved

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Andersson, TorbjörnPersson, Anders

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RadiologyCenter for Medical Image Science and Visualization, CMIVFaculty of Health SciencesDepartment of Radiology in Linköping
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