Impact of Iterative Bilateral Filtering on the Noise Power Spectrum of Computed Tomography Images
A bilateral filter is a non-linear denoising algorithm that can reduce noise while preserving the edges. This study explores the characteristics of a bilateral filter in changing the noise and texture within computed tomography (CT) images in an iterative implementation. We collected images of a hom...
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MDPI AG
2022-10-01
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| Series: | Algorithms |
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| Online Access: | https://www.mdpi.com/1999-4893/15/10/374 |
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| author | Choirul Anam Ariij Naufal Heri Sutanto Kusworo Adi Geoff Dougherty |
| author_facet | Choirul Anam Ariij Naufal Heri Sutanto Kusworo Adi Geoff Dougherty |
| author_sort | Choirul Anam |
| collection | DOAJ |
| description | A bilateral filter is a non-linear denoising algorithm that can reduce noise while preserving the edges. This study explores the characteristics of a bilateral filter in changing the noise and texture within computed tomography (CT) images in an iterative implementation. We collected images of a homogeneous Neusoft phantom scanned with tube currents of 77, 154, and 231 mAs. The images for each tube current were filtered five times with a configuration of sigma space (<i>σ<sub>d</sub></i>) = 2 pixels, sigma intensity (<i>σ<sub>r</sub></i>) = noise level, and a kernel of 5 × 5 pixels. To observe the noise texture in each filter iteration, the noise power spectrum (NPS) was obtained for the five slices of each dataset and averaged to generate a stable curve. The modulation-transfer function (MTF) was also measured from the original and the filtered images. Tests on an anthropomorphic phantom image were carried out to observe their impact on clinical scenarios. Noise measurements and visual observations of edge sharpness were performed on this image. Our results showed that the bilateral filter was effective in suppressing noise at high frequencies, which is confirmed by the sloping NPS curve for different tube currents. The peak frequency was shifted from about 0.2 to about 0.1 mm<sup>−1</sup> for all tube currents, and the noise magnitude was reduced by more than 50% compared to the original images. The spatial resolution does not change with the number of iterations of the filter, which is confirmed by the constant values of MTF50 and MTF10. The test results on the anthropomorphic phantom image show a similar pattern, with noise reduced by up to 60% and object edges remaining sharp. |
| first_indexed | 2024-03-09T20:52:22Z |
| format | Article |
| id | doaj.art-2ed7483203584bcfa9ce7e07d2ded3d6 |
| institution | Directory Open Access Journal |
| issn | 1999-4893 |
| language | English |
| last_indexed | 2024-03-09T20:52:22Z |
| publishDate | 2022-10-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Algorithms |
| spelling | doaj.art-2ed7483203584bcfa9ce7e07d2ded3d62023-11-23T22:30:30ZengMDPI AGAlgorithms1999-48932022-10-01151037410.3390/a15100374Impact of Iterative Bilateral Filtering on the Noise Power Spectrum of Computed Tomography ImagesChoirul Anam0Ariij Naufal1Heri Sutanto2Kusworo Adi3Geoff Dougherty4Department of Physics, Faculty of Sciences and Mathematics, Diponegoro University, Semarang 50275, IndonesiaDepartment of Physics, Faculty of Sciences and Mathematics, Diponegoro University, Semarang 50275, IndonesiaDepartment of Physics, Faculty of Sciences and Mathematics, Diponegoro University, Semarang 50275, IndonesiaDepartment of Physics, Faculty of Sciences and Mathematics, Diponegoro University, Semarang 50275, IndonesiaDepartment of Applied Physics and Medical Imaging, California State University Channel Islands, Camarillo, CA 93012, USAA bilateral filter is a non-linear denoising algorithm that can reduce noise while preserving the edges. This study explores the characteristics of a bilateral filter in changing the noise and texture within computed tomography (CT) images in an iterative implementation. We collected images of a homogeneous Neusoft phantom scanned with tube currents of 77, 154, and 231 mAs. The images for each tube current were filtered five times with a configuration of sigma space (<i>σ<sub>d</sub></i>) = 2 pixels, sigma intensity (<i>σ<sub>r</sub></i>) = noise level, and a kernel of 5 × 5 pixels. To observe the noise texture in each filter iteration, the noise power spectrum (NPS) was obtained for the five slices of each dataset and averaged to generate a stable curve. The modulation-transfer function (MTF) was also measured from the original and the filtered images. Tests on an anthropomorphic phantom image were carried out to observe their impact on clinical scenarios. Noise measurements and visual observations of edge sharpness were performed on this image. Our results showed that the bilateral filter was effective in suppressing noise at high frequencies, which is confirmed by the sloping NPS curve for different tube currents. The peak frequency was shifted from about 0.2 to about 0.1 mm<sup>−1</sup> for all tube currents, and the noise magnitude was reduced by more than 50% compared to the original images. The spatial resolution does not change with the number of iterations of the filter, which is confirmed by the constant values of MTF50 and MTF10. The test results on the anthropomorphic phantom image show a similar pattern, with noise reduced by up to 60% and object edges remaining sharp.https://www.mdpi.com/1999-4893/15/10/374bilateral filtercomputed tomographynoise power spectrum |
| spellingShingle | Choirul Anam Ariij Naufal Heri Sutanto Kusworo Adi Geoff Dougherty Impact of Iterative Bilateral Filtering on the Noise Power Spectrum of Computed Tomography Images Algorithms bilateral filter computed tomography noise power spectrum |
| title | Impact of Iterative Bilateral Filtering on the Noise Power Spectrum of Computed Tomography Images |
| title_full | Impact of Iterative Bilateral Filtering on the Noise Power Spectrum of Computed Tomography Images |
| title_fullStr | Impact of Iterative Bilateral Filtering on the Noise Power Spectrum of Computed Tomography Images |
| title_full_unstemmed | Impact of Iterative Bilateral Filtering on the Noise Power Spectrum of Computed Tomography Images |
| title_short | Impact of Iterative Bilateral Filtering on the Noise Power Spectrum of Computed Tomography Images |
| title_sort | impact of iterative bilateral filtering on the noise power spectrum of computed tomography images |
| topic | bilateral filter computed tomography noise power spectrum |
| url | https://www.mdpi.com/1999-4893/15/10/374 |
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