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Optimisation of tube voltage for conventional urography using a Gd2O2S:Tb flat panel detector

With the increasing use of computed tomography (CT) for urography examinations, the indications for ‘conventional’ projection urography have changed and are more focused on high-contrast details. The purpose of the present study was to optimise the beam quality for urography examinations performed w...

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Bibliographic Details
Published in:Radiation protection dosimetry 2010-04, Vol.139 (1-3), p.86-91
Main Authors: Zachrisson, Sara, Hansson, Jonny, Cederblad, Åke, Geterud, Kjell, Båth, Magnus
Format: Article
Language:English
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Summary:With the increasing use of computed tomography (CT) for urography examinations, the indications for ‘conventional’ projection urography have changed and are more focused on high-contrast details. The purpose of the present study was to optimise the beam quality for urography examinations performed with a Gd2O2S:Tb flat-panel detector for the new conditions. Images of an anthropomorphic phantom were collected at different tube voltages with a CXDI-40G detector (Canon Inc., Tokyo, Japan). The images were analysed by radiologists and residents in a visual grading characteristics (VGCs) study. The tube voltage resulting in the best image quality was 55 kV, which therefore was selected for a clinical study. Images from 62 patients exposed with either 55 or 73 kV (original tube voltage) at constant effective doses were included. The 55-kV images underwent simulated dose reduction to represent images collected at 80, 64, 50, 40 and 32 % of the original dose level. All images were included in a VGC study where the observers rated the visibility of important anatomical landmarks. For images collected at 55 kV, an effective dose of ∼85 % resulted in the same image quality as for images collected at 73 kV at 100 % dose. In conclusion, a low tube voltage should be used for conventional urography focused on high-contrast details. The study indicates that using a tube voltage of 55 kV instead of 73 kV for a Gd2O2S:Tb flat-panel detector, the effective dose can be reduced by ∼10–20 % for normal-sized patients while maintaining image quality.
ISSN:0144-8420
1742-3406
1742-3406
DOI:10.1093/rpd/ncq101