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Author: search.filters.author.Chanwimalueang, T.Subject: search.filters.subject.Backprojection

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    Small-sized computed tomography system with rotating gantry
    (2010-07-30)
    Jantanayingyong, V.
    ;
    Chanwimalueang, T.
    ;
    Srisuk, N.
    ;
    Pintavirooj, C.
    Small-sized computed tomography system with rotating gantry is presented in this paper. System calibration was performed before achieving the projection data. An object placed on platform was exposed by the x-ray every two degrees of rotating angle. Thus, 180 projection data were performed in this study. Finally, Feldkamp algorithm based on a 3D filtered backprojeciton was employed to reconstruct cross sectional images. The result shows that cross sectional images obtained from small-sized computed tomography were satisfactory. In conclusion, the small-sized computed tomography presented in this study is capable to construct the cross sectional images. Moreover, 3D model reconstructed from these cross sectional images will be performed in the future work.
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    Experimental investigation of arbitrary-orientation cone-beam X-ray tomography
    (2007-01-01)
    Chanwimalueang, T.
    ;
    Sangworasil, M.
    ;
    Pintavirooj, C.
    X-ray Computed Tomography is a technique to reconstruct an image of trans-axial slab of the object from a series of x-ray radiographs taken at a prior-known angle. Sequences of x-ray radiographs are served as two-dimensional projection data for a 3D tomography. The most popular Feldkamp Algorithm which is based on Filtered Backprojection (FBP) approaches has shown to perform well for 3D reconstruction. In the case of limited view, however, Feldkamp Algorithm suffers from star artifact. In these scenarios, an algebraic reconstruction technique such as the Simultaneous Algebraic Reconstruction Technique (SART) is engaged for reconstructing tomograms. Conventional x-ray computed tomography was implemented on a c-arm x-ray apparatus where the x-ray source and detector is capable of rotating to capture radiograph at any specific angle. The implementation of conebeam - geometry reconstruction algorithm, however, requires that the center location of the detector is accurately identified. Any slightly-missed alignment of the x-ray source or the detector could result in the error of the position of the center and hence the error in reconstructed image. Consequently, x-ray radiography tomography is normally implemented on a c-arm x-ray apparatus where the correct orientation of x-ray tube with respect to x-ray detector is achievable. The aim of this paper is to implement the x-ray tomography on a non c-arm x-ray apparatus where the x-ray source can be in any orientation with respect to x-ray detector. To determine the orientation, we take the radiograph of the reference transparent object, say the plastic box, of which the coordinate of the landmark, say the corner point, is known. The shadowgram of the box is analyzed to extract the coordinate of landmark image and to determine the orientation matrix using classical direct linear transform method (DLT). Once the orientation is known, modified conebeam tomography is performed to derived 3D reconstruction volumetric data. The experimental results demonstrated the potential of such method.
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    Miniatured computed tomography system and calibration
    (2006-12-01)
    Pititheerapab, Y.
    ;
    Chanwimalueang, T.
    ;
    Pintavirooj, C.
    ;
    Tosranon, P.
    In this paper, we focus on a miniature computed tomographic system with application in 3D modelling of bony structure of a small animal. Our system consists of an x-ray source, a rotating platform and an x-ray array detector unit. The rotating platform is controlled by a personal computer which can rotate the sitting object to arbitrary angle. The x-ray array detector is used to capture the 2D x-ray signal that traversing the object placed on the platform. The x-ray detector is an image intensifier tube of which the 2D image is coupled to the computer via a CCD camera. Feldkamp Conebeam technique is engaged for reconstructing tomograms due to its simplicity. Volume rendering technique together with the shading effects is performed on a stack of cross-sectional image to realize the data into 3D visualization. The algorithms are applied to the practical situation where a series of x-ray radiographs of an animal's bone are collected from the system. The 3D modelling of such bone is performed on the cross-sectional images reconstructed with Feldkamp Conebeam. The results are very satisfactory. © 2006 IEEE.