Yuki Ohsugi, Akihiro Narita, Masaki Ohkubo, Kenichi Sakai, Yoshiyuki Noto
{"title":"[一种测量螺旋CT扫描各向异性二维噪声功率谱的简单方法]。","authors":"Yuki Ohsugi, Akihiro Narita, Masaki Ohkubo, Kenichi Sakai, Yoshiyuki Noto","doi":"10.6009/jjrt.25-1528","DOIUrl":null,"url":null,"abstract":"<p><strong>Purpose: </strong>Recently, a new method has been devised to measure the anisotropic 2-dimensional noise power spectrum (2D-NPS) in computed tomography. The 2D-NPS varied with the X-ray tube angle θ in the helical scan; it was defined as 2D-NPS<sub>θ</sub>. However, the method requires many scans to obtain the 2D-NPS<sub>θ</sub> for each θ with less statistical variability and is laborious. In the present study, the 2D-NPS<sub>θ</sub> was assumed to be an identical anisotropic 2D-NPS that rotated around the origin of the spatial frequency domain in conjunction with the rotation of the X-ray tube. We defined the identical 2D-NPS as 2D-NPS<sub>rot</sub> and proposed its measurement method with fewer scans.</p><p><strong>Methods: </strong>The 2D-NPS<sub>θ</sub> (θ from 0° to 180° in an increment of 30°) were obtained from noise images acquired by a hundred scans of a water phantom. In the proposed method, the 2D-NPS<sub>θ</sub> were obtained from noise images by 2 scans, rotated backward around the origin by θ to generate the identical 2D-NPS, and averaged to generate the 2D-NPS<sub>rot</sub>.</p><p><strong>Results: </strong>The 2D-NPS<sub>rot</sub>, when it was rotated by θ, agreed well with the corresponding 2D-NPS<sub>θ</sub>. Absolute values of the mean and standard deviation of percentage errors of the 2D-NPS<sub>rot</sub> with the corresponding 2D-NPS<sub>θ</sub> at each θ were less than 0.70% and 6.12%, respectively.</p><p><strong>Conclusion: </strong>The proposed method was suggested to be valid for simple measurement of anisotropic 2D-NPS.</p>","PeriodicalId":74309,"journal":{"name":"Nihon Hoshasen Gijutsu Gakkai zasshi","volume":"81 4","pages":""},"PeriodicalIF":0.0000,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"[A Simple Method for Measuring the Anisotropic Two-dimensional Noise Power Spectrum in Helical CT Scan].\",\"authors\":\"Yuki Ohsugi, Akihiro Narita, Masaki Ohkubo, Kenichi Sakai, Yoshiyuki Noto\",\"doi\":\"10.6009/jjrt.25-1528\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p><strong>Purpose: </strong>Recently, a new method has been devised to measure the anisotropic 2-dimensional noise power spectrum (2D-NPS) in computed tomography. The 2D-NPS varied with the X-ray tube angle θ in the helical scan; it was defined as 2D-NPS<sub>θ</sub>. However, the method requires many scans to obtain the 2D-NPS<sub>θ</sub> for each θ with less statistical variability and is laborious. In the present study, the 2D-NPS<sub>θ</sub> was assumed to be an identical anisotropic 2D-NPS that rotated around the origin of the spatial frequency domain in conjunction with the rotation of the X-ray tube. We defined the identical 2D-NPS as 2D-NPS<sub>rot</sub> and proposed its measurement method with fewer scans.</p><p><strong>Methods: </strong>The 2D-NPS<sub>θ</sub> (θ from 0° to 180° in an increment of 30°) were obtained from noise images acquired by a hundred scans of a water phantom. In the proposed method, the 2D-NPS<sub>θ</sub> were obtained from noise images by 2 scans, rotated backward around the origin by θ to generate the identical 2D-NPS, and averaged to generate the 2D-NPS<sub>rot</sub>.</p><p><strong>Results: </strong>The 2D-NPS<sub>rot</sub>, when it was rotated by θ, agreed well with the corresponding 2D-NPS<sub>θ</sub>. Absolute values of the mean and standard deviation of percentage errors of the 2D-NPS<sub>rot</sub> with the corresponding 2D-NPS<sub>θ</sub> at each θ were less than 0.70% and 6.12%, respectively.</p><p><strong>Conclusion: </strong>The proposed method was suggested to be valid for simple measurement of anisotropic 2D-NPS.</p>\",\"PeriodicalId\":74309,\"journal\":{\"name\":\"Nihon Hoshasen Gijutsu Gakkai zasshi\",\"volume\":\"81 4\",\"pages\":\"\"},\"PeriodicalIF\":0.0000,\"publicationDate\":\"2025-01-01\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Nihon Hoshasen Gijutsu Gakkai zasshi\",\"FirstCategoryId\":\"1085\",\"ListUrlMain\":\"https://doi.org/10.6009/jjrt.25-1528\",\"RegionNum\":0,\"RegionCategory\":null,\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"\",\"JCRName\":\"\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Nihon Hoshasen Gijutsu Gakkai zasshi","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.6009/jjrt.25-1528","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
[A Simple Method for Measuring the Anisotropic Two-dimensional Noise Power Spectrum in Helical CT Scan].
Purpose: Recently, a new method has been devised to measure the anisotropic 2-dimensional noise power spectrum (2D-NPS) in computed tomography. The 2D-NPS varied with the X-ray tube angle θ in the helical scan; it was defined as 2D-NPSθ. However, the method requires many scans to obtain the 2D-NPSθ for each θ with less statistical variability and is laborious. In the present study, the 2D-NPSθ was assumed to be an identical anisotropic 2D-NPS that rotated around the origin of the spatial frequency domain in conjunction with the rotation of the X-ray tube. We defined the identical 2D-NPS as 2D-NPSrot and proposed its measurement method with fewer scans.
Methods: The 2D-NPSθ (θ from 0° to 180° in an increment of 30°) were obtained from noise images acquired by a hundred scans of a water phantom. In the proposed method, the 2D-NPSθ were obtained from noise images by 2 scans, rotated backward around the origin by θ to generate the identical 2D-NPS, and averaged to generate the 2D-NPSrot.
Results: The 2D-NPSrot, when it was rotated by θ, agreed well with the corresponding 2D-NPSθ. Absolute values of the mean and standard deviation of percentage errors of the 2D-NPSrot with the corresponding 2D-NPSθ at each θ were less than 0.70% and 6.12%, respectively.
Conclusion: The proposed method was suggested to be valid for simple measurement of anisotropic 2D-NPS.
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