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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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Improved-resolution x-ray array detector applied for SART fanbeam
(2006-12-01)
Angsuwatanakul, T.
;
Chanwimalueang, T.
;
Pintavirooj, C.
;
Sangworasil, M.
;
Lertprasert, P.
In this paper, we investigate the design and construction of improved-resolution x-ray detector. Our detector is an array of photo-transistors coated with gadolinium based phosphor similar that used in the x-ray cassettes and used in advanced medical CT detector. The x-ray array detector module consists of two main part: the detector frontend and data acquisition system. The detector frontend includes preamplifying, low-pass filter. The data acquisition system is served to convert the signal in to digital form and forward it to personnel computer. The application of the detector as a CT detector shows a promising result. © 2006 IEEE.
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X-ray -detector with CMOS sensor camera application of calcium denisty measurement
(2006-12-01)
Pititheerapab, Y.
;
Chanmalueang, T.
;
Rerksngaem, T.
;
Kitipol, C.
;
Pintavirooj, C.
This paper presented a design of an x-ray-detector using CMOS image sensor. The main components consist of CMOS sensor, taper fiber optic, and image intensifier screen, CMOS sensor offers various advantages including miniaturesized, low power consumption and cost effective. CMOS-based digital camera becomes hence very demanding due to its potential application in multimedia and information technology. To apply the CMOS sensor as x-ray detector, x-ray-to-visible light convector is required. Our key component of x-ray-tovisible light converter is an image intensifier screen mounted on the wider end of taper fiber optic. The narrow end of the taper fiber optic is coupled on the half-inch CMOS image sensor. In order to get higher image quality and system flexibility, more versatile CMOS image-sensor controller are preferable. Such complicate designs are made possible by the creation of entirely VHDL reconfiguration and programmable components- the socalled Field programmable Gate Array (FPGA). The designed x-ray-detector with CMOS sensor camera has been tested to capture a bony structure and ap-plied for calcium measurement. The result is very promising. © 2006 IEEE.
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3D modeling from radiograph with Conebeam geometry
(2004-12-01)
Kawikitwitcha, S.
;
Pintavirooj, C.
;
Tosranon, P.
;
Kiriratnikbm, T.
;
Anuntaseree, S.
In order to render 3D model of the bone, the stack of cross-sectional images must be reconstructed from a series of X-ray radiographs, served as the projections. In the case where the distance between x-ray source and detector is not infinite, image reconstruction from projection based on parallel-beam geometry provides an error in the cross-sectional image. In such case, image reconstruction from projection based on conebeam geometry must be exercised instead. In this paper, the Simultaneous Algebraic Reconstruction Technique (SART Conebeam) is engaged for reconstructing tomograms in case of limited views of radiographs. Compared with Feldkamp Conebeam technique, the SART Conebeam theoretically gives the better quality of image for the same limited set of projections 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 human femur bone are collected from a C-Arm x-ray apparatus. The 3D modeling of such bone is performed on the cross-sectional images reconstructed with SART conebeam. The results are very satisfactory. © 2004IEEE.

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