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Effect of vertical positioning on organ dose, image noise and contrast in pediatric chest CT—phantom study

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Abstract

Background

CT optimization has a special importance in children. Smaller body size accentuates the importance of patient positioning affecting both radiation dose and image quality.

Objective

To determine the effect of vertical positioning on organ dose, image noise and contrast in pediatric chest CT examination.

Materials and methods

Chest scans of a pediatric 5-year anthropomorphic phantom were performed in different vertical positions (−6 cm to +5.4 cm) with a 64-slice CT scanner. Organ doses were measured with metal-oxide-semiconductor field-effect transistor (MOSFET) dosimeters. Image noise and contrast were determined from the CT number histograms corresponding to different tissues.

Results

Significant changes in organ doses resulting from vertical positioning were observed, especially in radiosensitive anterior organs. The breast dose increased up to 16% and the thyroid dose up to 24% in lower positions. The noise was increased up to 45% relative to the centre position in the highest and lowest vertical positions, with a particular increase observed on the anterior and posterior sides, respectively. Off-centering also affected measured image contrast.

Conclusion

Vertical off-centering markedly affects organ doses and measured image-quality parameters in pediatric chest CT examination. Special attention should be given to correct patient centering when preparing patients for CT scans, especially when imaging children.

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Acknowledgments

Medical physicists Timo Kiljunen and Aki Kangasmäki are acknowledged for their help in image processing calculations and Vappu Reijonen for assistance in measurements. This study was supported by the State Subsidy for University Hospitals in Finland.

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Authors and Affiliations

  1. HUS Medical Imaging Center, Helsinki University Central Hospital, POB 340, Haartmaninkatu 4, 00290, Helsinki, Finland

    Touko Kaasalainen, Kirsi Palmu, Anniina Lampinen & Mika Kortesniemi

  2. Department of Physics, University of Helsinki, Helsinki, Finland

    Touko Kaasalainen, Anniina Lampinen & Mika Kortesniemi

  3. Department of Biomedical Engineering and Computational Science, School of Science, Aalto University, Helsinki, Finland

    Kirsi Palmu

Authors
  1. Touko Kaasalainen
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  2. Kirsi Palmu
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Correspondence to Touko Kaasalainen.

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Kaasalainen, T., Palmu, K., Lampinen, A. et al. Effect of vertical positioning on organ dose, image noise and contrast in pediatric chest CT—phantom study. Pediatr Radiol 43, 673–684 (2013). https://doi.org/10.1007/s00247-012-2611-z

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  • DOI: https://doi.org/10.1007/s00247-012-2611-z

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