Quantitative Evaluation of Metal Artifacts on CT Images on the Basis of Statistics of Extremes
| Autor: | Suguru Ueda, Takahiro Saika, Yoshifumi Ono, Shouta Hattori, Naomi Hashimoto, Kuniharu Imai, Shigetoshi Kitaguchi |
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| Rok vydání: | 2016 |
| Předmět: |
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Pixel Phantoms Imaging Image quality Statistics as Topic Streak General Medicine Imaging phantom 030218 nuclear medicine & medical imaging 03 medical and health sciences 0302 clinical medicine Gumbel distribution Metals Feature (computer vision) 030220 oncology & carcinogenesis Statistics Artifacts Tomography X-Ray Computed Extreme value theory Mathematics |
| Zdroj: | Japanese Journal of Radiological Technology. 72:402-409 |
| ISSN: | 1881-4883 0369-4305 |
| Popis: | It is well-known that metal artifacts have a harmful effect on the image quality of computed tomography (CT) images. However, the physical property remains still unknown. In this study, we investigated the relationship between metal artifacts and tube currents using statistics of extremes. A commercially available phantom for measuring CT dose index 160 mm in diameter was prepared and a brass rod 13 mm in diameter was placed at the centerline of the phantom. This phantom was used as a target object to evaluate metal artifacts and was scanned using an area detector CT scanner with various tube currents under a constant tube voltage of 120 kV. Sixty parallel line segments with a length of 100 pixels were placed to cross metal artifacts on CT images and the largest difference between two adjacent CT values in each of 60 CT value profiles of these line segments was employed as a feature variable for measuring metal artifacts; these feature variables were analyzed on the basis of extreme value theory. The CT value variation induced by metal artifacts was statistically characterized by Gumbel distribution, which was one of the extreme value distributions; namely, metal artifacts have the same statistical characteristic as streak artifacts. Therefore, Gumbel evaluation method makes it possible to analyze not only streak artifacts but also metal artifacts. Furthermore, the location parameter in Gumbel distribution was shown to be in inverse proportion to the square root of a tube current. This result suggested that metal artifacts have the same dose dependence as image noises. |
| Databáze: | OpenAIRE |
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