Journal of X-Ray Science and Technology - Volume 15, issue 4

Authors: Zhao, Jun | Lu, Yang | Jin, Yannan | Bai, Erwei | Wang, Ge

Article Type: Research Article

Abstract: Bolus-chasing CT angiography is an important new imaging mode for imaging cardiovascular structures and peripheral vessels. The adaptive bolus-chasing method implies a variable pitch spiral cone-beam CT scan. In this paper, we extend 2D-weighted, 3D-weighted and tilted plane FDK algorithms for variable pitch spiral cone-beam CT. Numerical simulation tests with high pitches and large cone angles are performed. Our results demonstrate that the tilted plane Feldkamp-type reconstruction algorithm shows the highest tolerance …to the data incompleteness, the 3D-weighted half-scan FDK algorithm is the best choice for the practical variable pitch cone-beam CT, and the exact reconstruction algorithms perform less satisfactorily when a dataset is incomplete. However, the exact algorithms can be used for high accuracy reconstruction offline if a dataset is complete. Our work may facilitate development of practical variable pitch helical cone-beam CT. Show more

Keywords: Computed tomography (CT), computed tomographic angiography (CTA), cone-beam, helical scanning, variable pitch, Feldkamp-type algorithms, approximate image reconstruction

Citation: Journal of X-Ray Science and Technology, vol. 15, no. 4, pp. 177-196, 2007

Authors: Prakoonwit, Simant | Benjamin, Ralph

Article Type: Research Article

Abstract: This paper describes a method for reconstructing 3D frontier points, contour generators and surfaces of anatomical objects or smooth surfaces from a small number, e.g. 10, of conventional 2D X-ray images. The X-ray images are taken at different viewing directions with full prior knowledge of the X-ray source and sensor configurations. Unlike previous works, we empirically demonstrate that if the viewing directions are uniformly distributed around the object's viewing sphere, then the reconstructed 3D points automatically …cluster closely on a highly curved part of the surface and are widely spread on smooth or flat parts. The advantage of this property is that the reconstructed points along a surface or a contour generator are not under-sampled or under-represented because surfaces or contours should be sampled or represented with more densely points where their curvatures are high. The more complex the contour's shape, the greater is the number of points required, but the greater the number of points is automatically generated by the proposed method. Given that the number of viewing directions is fixed and the viewing directions are uniformly distributed, the number and distribution of the reconstructed points depend on the shape or the curvature of the surface regardless of the size of the surface or the size of the object. The technique may be used not only in medicine but also in industrial applications. Show more

Keywords: 3D reconstruction, apparent contour, contour generator, epipolar, frontier point, multiview, space curve, surface points, surface reconstruction, X-ray

Citation: Journal of X-Ray Science and Technology, vol. 15, no. 4, pp. 197-222, 2007

Authors: Wang, Qiang | Liu, Zhao | Jiang, Huabei

Article Type: Research Article

Abstract: Diffuse optical tomography (DOT) is an emerging imaging modality for non-invasive brain functional mapping. The hemodynamic and metabolic images derived from optical properties are unique and complementary to those of magnetic resonance imaging (MRI) and positron emission tomography (PET). In this paper we present a procedure to optimize the number of sources and detectors as well as mesh size that can be used for image reconstruction in reflectance mode through a series of numerical simulations and …tissue-like phantom experiments where both the absorption and scattering images are obtained. In these studies, we also tested the system ability to image a target with small size as well as with low contrast relative to the background medium. Image results were quantitatively analyzed and discussed. Show more

Keywords: Diffuse optical tomography, three-dimensional, reflectance mode, quantitative, brain functional imaging

Citation: Journal of X-Ray Science and Technology, vol. 15, no. 4, pp. 223-234, 2007

Authors: Wei, Yuchuan | Yu, Hengyong | Hsieh, Jiang | Cong, Wenxiang | Wang, Ge

Article Type: Research Article

Abstract: Since Katsevich's work on cone-beam CT in 2002, a series of new reconstruction formulae for cone-beam and fan-beam reconstruction have been published. To understand these new results in a unified way, two schemes were proposed in the literature: one is based on the Radon formula, while the other on the Tuy formula. In the paper, we present a general two-step scheme for parallel-, fan- and cone-beam CT based on the inverse Fourier transform. We first derive …parallel-beam formulae and then translate them to the divergent-beam case via a standardized method. This complete framework not only provides a single mechanism for the deduction of most existing CT formulae but also generates new algorithms. Meanwhile, along the development of this new framework some minor flaws are identified and fixed in publications. Additionally, the traditional assumption that an object be compactly supported inside a scanning trajectory is no longer needed. Show more

Keywords: Computed Tomography (CT), Fourier analysis, convolution theorem, Dirac function, two-step scheme, instantaneous cylindrical system, three-step method, weighted back-projection (WBP), weighted Hilbert transform (WHT), frequency plane, dartboard function, Outward-homeward function, J function, odd/even extension, cone-beam, complete region, trajectory projection

Citation: Journal of X-Ray Science and Technology, vol. 15, no. 4, pp. 235-270, 2007