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Method for reducing noise in X-ray images by averaging pixels based on the normalized difference with the relevant pixel

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Abstract

A real-time digital filter for noise reduction in X-ray images is proposed. The filter is based on averaging of only similar pixels (pixels that differ only little) rather than neighboring pixels, which are averaged in conventional linear low-pass filters. The effectiveness of the filter was evaluated by computer simulation, where original images that were acquired by X-ray exposure were processed in accordance with the filter algorithm. The resulting images were evaluated in terms of the pre-sampled modulation transfer function (MTF), the noise power spectrum (NPS), and the lag. Comparison of the filtered and original images revealed that the NPS was reduced for the full range of spatial frequencies in the filtered image, resulting in a reduction of total noise power to about 1/9 the level in the original image with no degradation in the MTF or lag. The usefulness of the filter was demonstrated in fluoroscopic, digital subtraction angiography (DSA) and mammographic phantom studies. The filter was found to have the potential to reduce the patient dose by reducing the noise in dynamic as well as static X-ray images.

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Acknowledgments

The authors thank Kazuhiro Iinuma and Hiroshi Sasaki of the International University of Health and Welfare for their insightful suggestions. The authors are also grateful to Akihito Takahashi, Naotaka Sato, Shingo Abe, Hisanori Kato, Naoko Kuratomi, and Kae Aoki of the Toshiba Medical Systems Corporation for their cooperation in making valuable data available for this study. We wish to express our sincere thanks to the reviewers and the editors of this journal for their great support.

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Authors and Affiliations

  1. Toshiba Medical Systems Corporation, 1385 Shimoishigami, Otawara, Tochigi, 324-8550, Japan

    Masayuki Nishiki, Takuya Sakaguchi & Kyojiro Nambu

  2. Toshiba Medical Systems Engineering Co., Ltd., 1385 Shimoishigami, Otawara, Tochigi, 324-8550, Japan

    Kunio Shiraishi

  3. Division of Radiological Sciences, International University of Health and Welfare Graduate School, 2600-1 Kita-Kanemaru, Otawara, Tochigi, 324-8501, Japan

    Masayuki Nishiki

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  1. Masayuki Nishiki
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  2. Kunio Shiraishi
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  3. Takuya Sakaguchi
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  4. Kyojiro Nambu
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Correspondence to Masayuki Nishiki.

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Nishiki, M., Shiraishi, K., Sakaguchi, T. et al. Method for reducing noise in X-ray images by averaging pixels based on the normalized difference with the relevant pixel. Radiol Phys Technol 1, 188–195 (2008). https://doi.org/10.1007/s12194-008-0028-z

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  • DOI: https://doi.org/10.1007/s12194-008-0028-z

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