Journal Article

Optimisation of tube voltage for conventional urography using a Gd<sub>2</sub>O<sub>2</sub>S:Tb flat panel detector

Sara Zachrisson, Jonny Hansson, Åke Cederblad, Kjell Geterud and Magnus Båth

in Radiation Protection Dosimetry

Volume 139, issue 1-3, pages 86-91
Published in print January 2010 | ISSN: 0144-8420
Published online March 2010 | e-ISSN: 1742-3406 | DOI: https://dx.doi.org/10.1093/rpd/ncq101
Optimisation of tube voltage for conventional urography using a Gd2O2S:Tb flat panel detector

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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.

Journal Article.  3335 words.  Illustrated.

Subjects: Nuclear Chemistry, Photochemistry, and Radiation

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