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INTERIOR CT IMAGE GENERATION METHOD

外国特許コード F190009835
整理番号 S2018-0996-N0
掲載日 2019年7月24日
出願国 世界知的所有権機関(WIPO)
国際出願番号 2018JP004603
国際公開番号 WO 2018179905
国際出願日 平成30年2月9日(2018.2.9)
国際公開日 平成30年10月4日(2018.10.4)
優先権データ
  • 特願2017-061390 (2017.3.27) JP
発明の名称 (英語) INTERIOR CT IMAGE GENERATION METHOD
発明の概要(英語) Provided is a versatile method for generating an interior CT image which enables highly accurate image reconstruction via an exact reconstruction method even when a priori information cannot be used. This interior CT image generation method comprises the steps of: acquiring interior CT projection data by measuring only all quantum beams that pass through a region of interest (ROI) in an object, within the context of a CT measurement geometry; and acquiring parts of the entire projection data by measuring quantum beams from segments located outside the object, within the context of the CT measurement geometry, that pass through the entire object. The method further comprises a processing step involving exact reconstruction of the ROI on the basis of the acquired interior CT projection data and parts of the entire projection data.
従来技術、競合技術の概要(英語) BACKGROUND ART
First, CT (computed tomography) the interior of the principle will be described below. In addition, for the sake of clarity in the following used to measure X-ray CT in the case of the quantum beam is assumed, all of the other using the quantum beam can also be applied to the CT is apparent to those skilled in the art. In CT, for this purpose, such as a breast and a small test region of interest of the heart (ROI: Region of Interest) is sufficient that only an image, the image of the ROI does not need an external situation is assumed. In the usual CT, even in such a situation, as shown in Fig. 1 (a), not only line X passing through the ROI, to cover the entire object is irradiated with X-ray projection data are measured. However, does not pass through the ROI in an intuitive manner that the projection data of a straight line does not have information for the ROI, it is expected that unnecessary. Therefore, in order to eliminate such useless measurement, as shown in Fig. 1 (b), passes through the ROI only X-ray projection data and measured ROI to generate an image only of the CT system, referred to as CT in the interior. CT is interior in this way, (1) reduction of the amount of exposure outside of the ROI, (2) to reduce the width of the beam and the detector does not fall within the field of view, (3) the object to be photographed can be large, and the like advantages. In addition, the small field of view of the micro (nano) such as CT CT imaging device is enlarged, the field present beyond the interior of sample CT frequently occurs the situation.
In this way, in the interior CT, the measured projection data to generate an image from the problem of image reconstruction, can be formulated as follows. As shown in Fig. 2, shown by a solid line through the measured projection data is all ROI Ω, on the other hand, does not pass through the ROI Ω indicated by dotted lines in all the projection data is not measured. Then, if this incomplete projection data from, how the image of ROI Ω is to be strictly mathematically reconstructed, CT image reconstruction problem in the interior.
On the other hand, in the prior art interior CT, first, non-patent document 1: in, Natterer CT image reconstruction of the interior is a unique solution is not determined mathematically exact image reconstruction is proved that it is impossible. Therefore, an approximate solution for many years various research has been, an error occurs in the low-frequency component of the image to put into practical use and does not occur. For example, as an exemplary image reconstruction method, each of the direction of the projection data missing portion from the smooth function extrapolates the filtered backprojection (FBP: Filtered Backprojection) by a method of image reconstruction, algebraic reconstruction from incomplete projection data (ART: Algebraic Reconstruction Technique) an iterative and simultaneous iterative reconstruction (SIRT: Simultaneous Iterative Reconstruction Technique) method or the like is applied by the successive approximation method of, and the like have been studied (Non-Patent Document 2:-4 :).
Fig. 3 to, a typical artifact occurring in the interior of the CT according to an embodiment. Shading artifacts and distorted low frequency components of the image ROI image of the peripheral portion of the raised value of the cupping artifact frequently occurs. These prior research on, and only 2007 years to mathematically precise image reconstruction method is found, a new CT reconstruction of the image in an interior direction was born. The exact solution of these important keypoint in a word in summary, "interior of the CT projection data is an exact image reconstruction is impossible but, related to the object very little a priori information it is possible to mathematically precise image reconstruction is possible" and can be described.
Further, the development of the solution described above will be described and includes, first, the year 2007 Ye et al. (Non-Patent Document 5 :), the year 2008 Kudo et al. (Non-Patent Document 6 :), Wang et al. patent of 2008 years (Patent Document 1 :) is, as shown in Fig. 4 (a), the small region B in an arbitrary ROI Ω (a priori information area) in the image values if the a-priori information that is known, an exact image reconstruction of the ROI Ω is demonstrated. Next, Yu et al. in the year 2009 (non-patent document 7 :) and the year 2014 (Patent Document 2 :) Wang et al. patent is, as shown in Fig. 4 ROI Ω (b) the whole of a piecewise uniform value (a perfect constant value is a finite number of sub-regions can be made) if the, the image reconstruction is exact ROI Ω can be demonstrated. Further, Yang et al. in the year 2010 (non-patent document 8 :) is, to extend the approach of Yu et al., as shown in Fig. 4 (b), the whole of the piecewise polynomial value ROI Ω (finite order polynomial represented by the change by a finite number of sub-regions can be made) if the image reconstruction is exact ROI Ω can be demonstrated. Finally, the current 2017 year kudo et al. (PCT Application) and co-pending patent application (non-patent document 9 :) the article of Kudo is, Yu et al., Wang et al., in the method of the Yang et al. in a significant reduction in the a-priori information required for successfully, the small region B in an arbitrary ROI Ω (a priori information area) in the image as one piecewise polynomials or piecewise value if, the image reconstruction is exact ROI Ω can be demonstrated.
In addition, non-patent document 10: is, referred to as FBP method of Katsevich FBP image reconstruction method having the structure of the type, the non-patent document 11: is, in the FBP method of Katsevich filter have symmetry in the corrected projection data, then, the non-patent document 12: is, phase CT 2 is significantly different to the one of the present principles are shown.
  • 出願人(英語)
  • ※2012年7月以前掲載分については米国以外のすべての指定国
  • UNIVERSITY OF TSUKUBA
  • 発明者(英語)
  • KUDO Hiroyuki
国際特許分類(IPC)
指定国 National States: AE AG AL AM AO AT AU AZ BA BB BG BH BN BR BW BY BZ CA CH CL CN CO CR CU CZ DE DJ DK DM DO DZ EC EE EG ES FI GB GD GE GH GM GT HN HR HU ID IL IN IR IS JO JP KE KG KH KN KP KR KW KZ LA LC LK LR LS LU LY MA MD ME MG MK MN MW MX MY MZ NA NG NI NO NZ OM PA PE PG PH PL PT QA RO RS RU RW SA SC SD SE SG SK SL SM ST SV SY TH TJ TM TN TR TT TZ UA UG US UZ VC VN ZA ZM ZW
ARIPO: BW GH GM KE LR LS MW MZ NA RW SD SL SZ TZ UG ZM ZW
EAPO: AM AZ BY KG KZ RU TJ TM
EPO: AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR
OAPI: BF BJ CF CG CI CM GA GN GQ GW KM ML MR NE SN ST TD TG
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